Ask HN: How do you deal with large missed opportunities?

How do you deal with large missed opportunities? Recently this has been eating me up. I have been dwelling on a couple of missed financial opportunities which would have been life-changing for me. I just can't seem to get over it, the ‘what ifs?’ keep me up at night. I’ve Googled and read advice about how to deal with this and the one upside is that I've identified the opportunity once, the next time I should be able to capitalize on it. This still doesn't help much :-/