I can relate but also support that it probably was not really a mistake.
Other than having a kind of systematic approach, such as trying not to edit wardrobe when you're tired, grumpy, feeling body-bad or something; maybe having a holding zone for 2nd thoughts; remembering the seasons, and not to go crazy purging sweaters in the summer--then I think we just have to move on.
I think of the alternatives and where I want to be--I don't want to have closets stuffed full of items not worn but waiting to see if they'll come back into style or use. I think it's fine to do this with a few items selected for fit, rarity, or that you like all the time, but will wear more or less when the trend is "up" vs. down.