It’s not universally true I admit, but on the whole aren’t regrets usually about the things we didn’t do, rather than the things we did? From the trivial (I wish I’d used that turnip in the stew on Saturday, now it’s gone mushy) to the ones that threaten to overwhelm us (why didn’t I patch it up with that friend/relative/former lover? Now they’re dead and it’s too late).
I can’t help you with the big ones (though really, would it kill you to write to your Aunt Phyllis and forgive her for taking those curtains you always liked from your grandmother’s house?) but the ones that are writing-related, I might be able to stick my oar in. Go look down that list of stories you always meant to write, the list you keep carefully locked away in case anyone either steals your idea or laughs at your ambitions. Now cross off the ones that have been on there so long you can’t remember quite what you were getting at, or you can but you no longer care if you (or anyone else) writes them.
Depending on age, imagination, or previous bursts of industry you’ll be left with a list of ideas ranging from about half a dozen to more than you’d care to count. Pick one, either at random or by the mood you’re in, or to fit a theme deadline that’s coming up. Now write it. What’s stopping you? OK you might have intended to write an epic novel on that one, but what happens if you try and distil it into flash fiction? Does it clarify some ideas, get the juices flowing, give you some description or dialogue you could use in the epic novel, or does it even tell you that this idea doesn’t have the potential you thought it did?
Repeat regularly (I’d suggest weekly, but life intrudes sometimes) until you’ve worked through the bulk of your list (which I’m imagining is ever-growing). Look at what you have – have any of those short stories satisfied you on that theme? Could you polish up that draft and try placing it somewhere? Has it reawakened your desire to write that novel, and sent you off researching? Or was it just a writing exercise that sent you off on a different tangent altogether?
I’m going to attempt to take my own advice on this; my bits file is ridiculously full and I can’t imagine being able to use all those ideas if I wrote for a lifetime and never added to it after today. However, if instead of glancing through, finding it too daunting and going to do something else, I write a 500 word story that’s pleasing in itself and uses my idea without quite doing all that I’d originally intended, that has to be a better outcome. And just because I’ve written a short story about it now, doesn’t mean I can’t write a novel next year.