I feel like I learned it was "over" a few times in my life.
I realized I'd always be miserable at about 12 years old, because I hated school with an unwavering passion and was overly sensitive about family matters. I decided the best I could do was to live in a fantasy world and otherwise reduce pain. Also puberty seemed to rob what was left of my good moods.
At 16 years old I saw my life's passion being denied me, despite my best efforts. My belief that I could be anything I wanted if I worked hard enough was crushed, and I've been scarred by that realization ever since. Also: medication only provided mild relief.
At 23 years old I understood nothing would ever change, and all I wanted was to die, but I was too chicken to do it. The was about the worst time in my life. I got really fat and became obsessed with suicide.
At 29 years old I saw that nothing I could do (looksmaxxing etc) would entice the fairer sex to play with my wee-wee.
Now I'm 36, and it seems the last bit of discipline and hope I worked from is about gone. I can't diet anymore, or work-out, or practice music, or do anything productive.