Debilitating angst, severe heartbreak and incredible poverty all prepare for a happy 30’s! Maybe add some unemployment in there.

There's nothing you [i]have[/i] to experience in your 20s. Life is one long journey, with many ups and downs, joys and tears, and many memories... Just live and try to enjoy yourself

Childbirth

Theres no solid anything...our lives and experiences are totally unique and personal

I’d just say for most people hopefully what was cool to do at 18 isn’t at 30. If it is in a lot of cases maturity isn’t quite where you’d expect.

I don't know about "must", but here is something that happened to me.

I went through high school and college with a certain self-perception of what I looked like to others. During my 20's, I tried to hold onto that image in my mind, only to be confronted with the image in the mirror which showed me that I was "aging".

But one day, it hit me: "Stop thinking of yourself as an old 20-something. Think of yourself as a young 30-something." And when that thought hit me, I could almost see the face in the mirror change. It was as if I had learned anew how to regard myself.

Of course, this was not just about "looks". It was an acceptance that I was moving on to a new stage of life. But that realization was actually accompanied by a "sudden shift" in how my mirror reflection looked to me.

This has happened to me over and over, in my late 30's, late 40's, etc.