I think a lot (maybe not all) of these only turn out to be regrets in hindsight. Some are polar opposites of each other.
Some regretting choosing career over settling down, some regretting settling down over career.
Some regretting some man they once thought was wonderful but now they can't stand and others regretting never pursuing that man they thought was wonderful.
I would love to have travelled more in my 20s but poor mental health and life circumstances meant it never happened. I'm doing all I can now to make sure I get to see the places that I want to see. Sure it won't be carefree gap years, it will be for much shorter periods and my family will be in tow, but it is something I can do to scratch that itch and live out that dream. Tbh with my MH in the drain and my tendency towards substance abuse/self-destruction I'm not sure travelling would have been the idealised experience I sometimes imagined.
Anyway. Very long-winded. But I'm not sure it's possible to get through life without some elements of regret or wondering. Hindsight really is 20/20.
Maybe worth considering what you can do now, although i appreciate it's not always possible or easy, contributing more to the pension, retraining, getting therapy, living healthier etc.