So, I dunno enough about your life to say where you have talent, but I did want to mention something. You are upset about this, or upset about life in general, you've been quite upset lately. There was a period before this where you weren't upset, you seemed confident, and happy and didn't appear to fail at anything really then. But now that you're upset, you feel you're failing at everything and you feel you failed your whole life, but if I had talked to you when you were happy, I'm not certain the response would be the same.
You see, when you're upset you tend to focus on all the negative aspects of life, which makes you more upset. It's a self-defeating loop and it essentially means "when you're sad you think of sad stuff", this happens with everyone, not just you, but I've seen it and observed it happen with a lot of people. The question is, did this sad stuff cause you to be sad? Well, some of it probably did yes, but in this scenario I think you being SAD has caused you to think of all the sad stuff that has happened. In which case it's important to realize that you are focusing on only the negatives, just when you start thinking "I'm such a screw-up, because I didn't cut pies properly" maybe realize that "I'm only focusing on the negatives" and a positive is "I actually have a job and not only that, I haven't been fired from it, I'm not under probation of any sort and so forth" If that is true, then your employer obviously doesn't think you're a screw up. Same thing with the intelligence thing "People don't consider me intelligent, but that's focusing on the negatives, the school system assures me I'm not unintelligent because I graduated high school and I'm in college, something that a lot of people don't even get to!".
So just remember, you're focusing on the negatives because you're sad, remember that there are positives as well, you just need to try and focus on them. It''s hard to do but just keep reminding yourself (don't even question it, you can I mean, but just try and remind yourself constantly either way) that you are only focusing on the negatives, that you are saying "I am focusing on the negatives" and perhaps then you might look for some positives.