Condolences on the loss of your father, OP.
I wish I had taken up more of the opportunities to sleep with gorgeous men, when I was young, fit and gorgeous myself - instead, I was a total and utter prude. I turned down a threesome with a stunning Australian man I knew well enough to have felt safe with, and his friend, and I really regret that! Obviously I am alive and something awful could have happened had I been reckless and slept around, but I still think I was way too sheltered and missed out on a lot of good times.
Gotten on the property ladder sooner. And never sold it.
I wish I had not gotten married. Or at least, not married the man I did. I wish I had understood the legal contract of marriage, and that I would lose my house. If I were to have gotten married, I wish I had married a richer man, or, had kids with a richer man. At least I'd be divorced with a roof over my head, not in the messy predicament I am in now. I can't see how I will ever get on the property ladder again, and I am petrified for my future in retirement.
I did travel a fair bit, but I wish I had done so much more.
I wish I had tried skiing and snowboarding - I am too old now.
I wish I had bought a house in central London, and raised my kids there.
I wish I knew that I could have had a career as a dancer, rather than the academic route I was lead to believe was the best route to success.
I wish I had insisted to the ex that we not move around so much (at all!) once I had DC1. I have been uprooted so much as a trailing spouse, and in retrospect, it was disastrous.
Lots of mistakes, some I'll never recover from. Still, I am alive, and my children are healthy and ok, so I do count my blessings.