Throughout the course of "my twenties", I was psychologically (not rationally) convinced I was invincible, and I more or less behaved like my body could not fail me in any serious way, regardless of the extremes to which I pushed it. I'm aware this disposition was unwise.
So I recently entered the fourth decade of my life and went to the doctors and found that I am not, in fact, invincible. This is a hard truth that I don't like. Reason let me know it when I was younger; time made it real, and reality has impinged upon my delusions and upset me.