What makes you wistful?

I do not believe in regrets, but once in a while, I get wistful.

If you can’t or don’t or won’t link, Websters says: “having or showing sad thoughts and feelings about something that you want to have or do and especially about something that made you happy in the past”.

I, personally, do not believe in regrets, but occasionally I remember great things in the past that I could have build upon if I’d been a little more experienced.