When I was about 18 and in high school my depression hit so hard that I had Cs and Ds in every class. I was "smart" but I didn't really care about school until I was in danger of failing. After I started caring again I managed to pass all of my classes except English. I flunked that and I didn't walk. Then I went to summer school. I was so messed up that I failed that too. Then I had to repeat at the same school I failed at... Almost failed again...

Why? Because I didn't care. It didn't matter that I was smart or anything like that. I skipped grades like stoners skip class. But I felt like nothing in life was important anymore and things went downhill. I failed because I didn't believe in myself or anyone else. And a lot of kids your age think that it's all about who's smarter or faster or whatever but it's not. The smarter person doesn't always get the job and the fastest person doesn't always win the race. But the one that pushes hardest usually does all those things. All you need to do is look at the graduate employment rate if you need proof.

So maybe you just lost your inspiration to do what you're doing and that's what you need to find.