You may or may not have chosen to be born, but all indications point to "acting like you did"--i.e., injecting your own existence with meaning by assuming you had a purpose for coming--being more beneficial to your well-being than a more nihilistic attitude.
http://yourmeaninginlife.com/blog/you-didnt-choose-to-be-bornbut-should-you-act-like-you-did
You can always find a reason to complain, and you can always find a reason to be grateful. The former will lead to a miserable life; the latter will lead to a more pleasant life.
https://yourmeaninginlife.com/blog/it-will-always-be-something
There are many misconceptions about how important growth is to your life, from what kinds of growth are possible, whose growth is meaningful, and how growth is meaningful even in the face of endings and death.
https://yourmeaninginlife.com/blog/misconceptions-about-growth-oriented-meaning