A time when you start feeling old because you've been out of high school more than 5 years (you don't still take the same chances you did in high school), but you don't know yet that in 10 years, you won't feel as old as you did in your mid twenties, even though you'll actually be a lot older than you were in your mid twenties.
Your mid 20s isn't an easy time because you haven't lived long enough to know that if you find your rythym, even if you've done it before more than once, it isn't just luck, or who you were yesterday.