We have the penchant to feel more regretful with things we didn’t do than things we did but failed.
The stock that you vacillated to purchase or not purchase doubled its value within a few months. You now have the intense regret for not purchasing it.
The major that you chose for your college turned out to be a mistake that you couldn’t finish the college. Most people would feel regretful, but not as much as the former scenario even though you have lost years of opportunity cost that you can use to study the right major.
Unconsciously, our mind contrives reasons to justify every action we do than what we don’t do.