My personal experience has been that life gets better as you get older. At least that is how it’s been so far, Boruch Hashem, bli ayin hara. I am only talking about from age 18 onwards. Before that, it was the opposite way around for the most part.
The older you get, the more resources you have. In many areas – Emunah, self-confidence, social skills, coping skills, friendships, practical skills, knowledge of various kinds (Torah, practical, wisdom, etc.). You also have more control over your life than you do when you are younger.
Adolescence is the hardest – you have few resources and no control over your life.