This question already has an answer here:
I am about to submit my PhD thesis in 4 months and have to move on from being a student. I am already 30 (so a sort of mid-life crisis catching up). I feel that I made a really big mistake in entering academia and should have not gone into masters 7 years ago. I feel incompetent with no area of expertise. I am a mathematically and technically weak PhD student in a field of research where being proficient in analytical and theoretical analysis is the only required skill for research. I think I am technically screwed up.
My question is just vague. What should I do, and are my future prospects as limited as I foresee them to be?