I only realized in retrospect that it was burnout. I "felt fine" at the time. I remembered being passionate about things in college but it seemed like I was just too busy for that kind of thing anymore. Sometimes I'd sit and think, "hmm, strange that nothing seems to excite me anymore, maybe that's just what getting older feels like."
I knew I felt weary, but everyone around me seemed to feel the same. I was honestly surprised when the color came back. I was almost too busy to notice it was missing.
Now that I know how my own burnout symptoms manifest, I can keep an eye on my stress and work-life balance to make sure I don't get so far gone again.