This is a copy of my reply in another thread:
badRobot wrote:
You are not alone. This happens to a lot of people, this happened to me as well.
I was one the best students in my university, I was sent to other cities to represent my university in international contests, several times our team ranked top 3.
My interest in my subject was very intense, I would neglect everything else and spend days and nights doing one thing I enjoy. But near graduation I got depressed and completely lost interest in my field and studying in general. I was forced to take a year break. Luckily I recovered almost completely by the next year and managed to complete my thesis.
Then I started my post-graduate. At the same time my interests restored and I attended a lot of events around my interests. I've met my girlfriend at anime convention in a public library, later we moved in together.
I had a great job, I loved it and my post-graduate work was extremely fulfilling, it was a perfect match for my interests. I would neglect everything else and work on my work tasks during the day and on my post-graduate during nights, I was proud of this lifestyle, I made me feel like my life is dedicated to my cause. Eventually I got severely depressed, snapped out on my colleagues, I lost interest in my job and was feeling disappointed all the time, I quit my job. Couple weeks later I broke up with my girlfriend because I believed she didn't share my dedication and was undermining my success. Now I understand none of my beliefs about my job and my relationship were true.
Every single time this happened I've completely lost interest in anything, in my favorite music, movies, hobbies and work.
At some point I discovered I'm on the spectrum and believed this is why this all happening to me. I'm autistic, people don't understand me, I don't understand people, they make my life miserable and no wonder I stop doing things I used to like and end up depressed. Right? No, I was wrong.
Luckily, one of my friends invited me to a hiking trip and didn't take no for an answer. I've immediately felt MUUUUUCH better when I returned from it and it made me think. I started digging information and health become one of my intense interests and hobbies.
Now I have much deeper understanding of my condition and looking back I see exactly what happened, what I could do to prevent it from happening every time.
Now I have a lot of interests and pick up a new hobby once in a while. What's interesting, now I've lost fear of trying something new, challenging myself. Now I have a mental framework to approach some things I used to find really intimidating and too hard to even start.
I'm not special in this regard, I don't have innate strong willpower or something, I'm not smarter than most people, absolutely everyone can change for the better knowing exactly what to do and doing it.
So don't worry, you interests will return, it's a matter of time. But there are things you can do to bring this change intentionally instead of waiting for it to happen to you.