Over the years I've often seen people saying stuff like "your 20s are the hardest; it gets so much easier in your 30s and beyond!" but I think this assumes many things. Namely that these people suffering in their 20s are still on a path towards a more comfortable existence in their 30s, be that through career progression, education, gaining life experiences, forming relationships, building a family etc. These steps are assumed to be taking place in the background.
From my own experience it is quite possible to lose many years of one's life doing nothing and to watch the year markers pass by with nothing changing. Suddenly you're 25, 30, beyond, with nothing to show for it because those years were spent doing nothing. The age number itself means little, it's more to do with how the years are filled.