Everything and Nothing. Leaving the comfort zone more often is something which will make you grow. And I didn't do that in the past. Bit of a life story:
I'm 36 now. When I turned 22 in 2008, my mom surprised me with her having sarcoidosis, a disease which will turn functional cells into non-functional ones. Quite an issue when it starts in your lungs. A year later, my father surprised me with him having cancer.
Long story short, they passed away in 2013 and 2017. I should also mention that I have four younger siblings. I raised my little sister until the beginning of 2020, when she turned 18. And then, the pandemic hit.
I wish I'd talked more to my dad. I wish I would have been more socially active, would have gone on a fishing trip with him. Worked on the car. You know? Things you do with your dad. Instead, I buried myself knee-deep into coding. I read books. But I missed life.
And I accumulated debt. Oh, am I in debt right now. 46k still left to pay off, with which I'm struggeling.
And the path I choose? Up to today, I don't even know if it's the right one. I'm a coder. But from time to time, I need external validation. I need "the stage". And I love to teach other people stuff. Working from home, I realized that I don't have any problem talking directly into a camera. Just recently, I moderated a panel discussion with 7 participants and an audience of ~100 people. I wasn't aware of me being able to do that. But there were people in my company who believed in me and said "Do it!" and I decided to leave my comfort zone.
That was maybe the best feeling I had for a long, long time.
tl;dr:
a) Avoid the debt trap
b) Spend time with your loved ones, as much as you can. Grow bonds.
c) Leave your comfort zone. Experiment. And never be afraid to fail.