After regrettable experiences, I used to think, if I knew it was gonna be like this, I wouldn't have done it.
But I've come to the realization that this model of thinking doesn't always work. There is discontent/negative utility from wondering what could have been. This means even if I didn't do it, I would be wondering about the potential outcome and that wondering/uncertainty could be worse than the outcome itself, or at the very least, disrupt the previous decision calculus.
A recent example is trying a dessert place. I was debating trying a new dessert place. On one hand, I like dessert. On the other hand, dessert isn't free and I was trying to eat more healthy.
I tried and dessert and, turns out, it wasn't good. Normally, you might think dang, if I knew it was going to be mid, I wouldn't have gotten it. But you'd be forgetting that in the counterfactual—the world where you don't try the dessert—you'd be fantasizing about the potential positive utility from the dessert. In that world, you don't know what the dessert tastes like. What if it's amazing?
That uncertainty and wondering slowly gnaws at you. After walking past the dessert spot, you become acutely aware of how hungry you are and how much you're craving carbs. You spend the rest of the day lamenting your decision and wondering how different your day could have been.
The moral of the story, if there is one, is that the "right" decision is the one you make. The roots of the word "decide" actually come from the Latin word decidere, meaning to cut off (thank you Manansh for teaching me this).
When you decide, you cut yourself off from a potential world. It doesn't exist anymore. The only things that are real are the benefits of the decision you made. The beauty of this is you can make up what the other world would have been. So the next time you skip (or don't skip) dessert, you can rest easy knowing it was the right choice.