In This is How You Lose Her, Junot Diaz writes about all the trials and mishaps of his lead character's (who undoubtedly is based on him) relationships with family and women. The complications, mistakes, karma, and dickishness (TM- MyTien Huynh, yes) just turns out to be funny.
The trials and failures of human relationships, and the awkward interactions between people is painful but yet those mistakes, the saltiness, the bitterness, the 'oh my god, I can't believe I did that' is so funny in hindsight.
If I were to write an autobiography chronicling my relationships between 16 and today, I would find it funny too. Not necessarily because anyone was a mistake (people aren't mistakes), or any visceral pain was so powerful or unexpected, but simply because there was a slew of snowballs that I wasn't ready for, yet I took anyways, and slid on my face, and got some scars, got some jadedness and sarcasm in my personality, and all of that creates a funny lived experience most adults have to deal with. And to be fair, I threw some snowballs too. We all do.
When a person's fairy tale goes awry, his/her reaction and how pissed a person gets about it, how stupid they look or feel, how pathetic they become is hilarious. You can prepare to a certain extent but life also has it's plans for you.
It's a reminder that no one ever gets to their perfection, they continually keep trying. Sometimes they fall on their face, sometimes they fall on their ass, sometimes they're not proud of the shit they do but they did it, and it's history now.
The painfully funny reality is that people will move forward trying to avoid writing more 'funny' chapters in your autobiography but they inevitably will. It makes people bitter and complicated and unique and all of those things in the long hall are wonderful.