Fixing as you go along.

There are times, while cooking, when you realise that everything hasn't quite turned out like you'd expected. You thought you could eyeball the recipe (more or less), and did so. All of a sudden, the ratios are all off, your tongue and brain are both berating your eyes for missing the mark, and it looks like everything is about to go belly-up. These moments can be frustrating and disheartening, especially to a new cook. The trick is to not panic. Or realistically, to panic, but recover quickly.
There's a couple of things you can do before you start cooking to avoid disasters in the first place. There are also things that cannot be salvaged, and should not be salvaged. If you've burned your spices to an absolute crisp, just toss them out, and start over. Better to lose a few cents in off spies than to go through with the whole thing and end up with a horrible tasting disaster that now cost you a lot of time and effort. If your oil smells rancid, or when you start up your skillet, you smell something rancid, throw out that fat, and start over. Clean the pan thoroughly, and try again.
Rancid oil cannot be covered up, no matter how much you'd like to think so. I was once using a cast iron skillet that I hadn't touched in a while. I also foolishly left a small pool of oil on it for too long. Instead of doing the sensible thing and cleaning it off first, I made up a batch of dosa. A rancid smelling batch of horrible dosa. A rancidness that just did not fade, no matter how many changes of oil I'd put in. Once I gave the skillet a good scrubbing, all was well. But then, there was a batch of 15 dosa that had to go in the bin, because I'd been too foolish to stop while I was ahead, and just start over.
This goes double for burnt spices. I'd started off a lemon rice, and let the mustard seeds go too long. They weren't just popped, they were little blackened bullets of charred mess. I bull-headedly kept going, and burnt the hell out of the cumin seeds and the urad daal too. Y'see, when the pan is too hot for the one spice, it follows that adding more spices will mean that you have even more burning, and not less. I don't know /where/ my head was. In any case, I managed to thoroughly burn the seven hells out of the spices. I kept going.
Bad move.
The final dish tasted absolutely inedible and awful. It wasn't worth salvaging. It couldn't be salvaged. If I'd had any sense, I'd have stopped the instant that I saw the oil smoking too much. If I'd had less sense, I'd have stopped when I realised that the mustard seeds went from just a little heavily browned (which is fine) to outright black char. I could have pitched the spices, and been OK with a fresh pot of oil and a bit more spices. Sometimes, it's important to know when to stop, so that you can save yourself much more pain down the road.
Or, there was the one time I'd made a walnut date crust. It seemed awfully fatty when I was putting it into the pie pan. I didn't listen to my instincts, and stop. I just kept going. In went carefully layered fruits, arranged in concentric circles, with a bit of sweetener in between. The whole thing was a disaster and a half. I should have realised that when the recipe says soaked DATES, that date puree will not do. When the crust felt too fatty, I should have stopped, re-calibrated things, and kept going.
Long story short, before you take any of these tips on how to save your almost disasters, please understand that I'm not condoning you keep chugging along when things have gone to hell and back. Know when to stop. It'll save you a lot of tears.
But all that aside, there are times when things aren't going quite according to plan, when you can stop yourself, tweak a bit here and there, and move forward. It'll work out just fine in the end.
Your hummus is way too thin, and you're out of chickpeas.
The prevention for this is to set aside about a small handful of chickpeas, while you make the hummus. If your hummus is just fine, and perfectly thick, just blend them separately with a bit of your hummus, and mix the lot together. Far more frequently, however, you'll need to add more chickpeas, because you overshoot perfect and creamy. In fact, it's so common that I've powered through huge amounts of tahini in doing so. That's the fix-it solution, by the by. Tahini. Lots of it.
Suppose you're making hummus, and your processor is merrily chugging along. It's taking too long for your liking, so you splash in a bit more fat or water to smooth things along. The processor kicks up speed, and demolishes the stuff in it. You open the lid, and the hummus isn't thick and creamy but droopy and runny. You promised to bring hummus! If you don't bring hummus, they'll take away your vegan card! (It's true. By the by, if anyone wants to know what to get your favourite vegan blogger with a sense of humour about his own veganism, get him that t-shirt. It's wicked cute.)
Start, bit by bit, adding more hummus, almonds, walnuts, pecans, pistachios, or any other toasted nuts you like. It'll add a richness and creaminess that will make your hummus taste far superior to other hummus that folk have eaten. It thickens up quite beautifully If you want to avoid over-adding water, there is another trick you can use to make the processor cream the chickpeas easier, and not have to add too much water.
Cheat and use a little bit of white beans in your mix. For every 2 cups of chickpeas that you soak overnight, soak 1/2 cup of white beans in a separate container. (Or, do what I do and soak the full 2 cups of white beans, and follow up the hummus making with rosemary & white bean dip). Essentially, you're looking for a 4:1 ratio of chickpeas to white beans. For whatever reason, the white beans seem to cream up much easier than the chickpeas. I don't know why. I discovered it by accident, when I made a batch of hummus after making a batch of white bean dip (and not clearing out the last 2 inches or so of white beans left in the processor).

Your roux based sauce is too thin. 
The way to prevent this is to carefully measure out the fat and the flour, and make sure that the liquid is proportionate to the colour of your roux. Here's an easy way to remember how to work your roux: 1 TB of fat and 1 TB of flour will thicken up 1/2 cup of liquid when the roux isn't too dark. This means that you'll need to actually measure out a level tablespoon of fat and a level tablespoon of flour, so that you've got the proper thickening going down. The reason that I mention the darkness of the roux is because the darker roux don't tend to thicken as well as the lighter ones. This is why it's best to work best with medium low heat, and gradually get to the colour you want, so that you don't end up overshooting the mark, and get something that doesn't thicken correctly.
Suppose that you did indeed overshoot the mark, and your gravy/cream sauce/sauce is too thin. Don't use a slurry of flour and water. It'll require that you cook the thing for much longer to work out the raw flour taste. Don't use a flour/fat mixture that you whisk in. Just make more roux. It'll be fine. Get out a separate little pot, throw in a bit more fat, and a bit more flour, whisk for a couple of minutes to cook out the raw flour taste, and whisk in the too-thin sauce, and pour the mixture back into the thin sauce. Bring it to the boil, and you're set.
If you've run out of flour, whisk a bit of cornstarch with some water (about 1 TB of water with 1/2 TB of cornstarch), and pour that slurry into the thin sauce. The reason that cornstarch will work well is because cornstarch comes up to cooked stage much more quickly than flour.

Your rice isn't cooked to done-ness (while some of the grains are). 
This happens from time to time, when the water to rice ratio is off. It's happened more times than I care to remember. What I tend to do is add a bit more water, put it into a pyrex dish, and microwave it (covered) for about 10 minutes. That's usually enough to get the last few stubborn grains to finish cooking. If they're still not done, sprinkle in a bit more water, and let it go another 7 minutes in the microwave.
The reason that I suggest using the microwave as opposed to the stove or putting it back in the rice cooker, is because the microwave tends to cook rice on the drier side. The stoves and rice cookers tend to need more liquid, and tend to steer the whole mess towards a mushy mass. The microwave, on the other hand, tends towards a bit drier.

This is, of course, just a start. There are plenty of other things that can go wrong along the way, and I'm sure I'll mention more in future. I wanted to mention these simple things, so that you all can get more confident in your kitchen.