I think we all feel like that every once in a while.
What you've got to bear in mind is; you've young and have your whole life ahead of you. Standard advice, I know, but it's also the truth. Very few people know their strengths so early on in life, it's only later when you experience more that you get to become familiar with yourself.
Keep trying new things, work on what you need to do already, study as hard as you can, but also make sure you don't put too much pressure on yourself and enjoy life.