This is not going to be a textbook philosophical treatise, more just the view from the hangover after a big night out.
There is an oft-quoted saying - that people regret more of the things they didn't do than the things they did do ...
but like all oft-quoted sayings, that's a load of context-specific twaddle.
Sometimes you might think that you'll regret not going somewhere - but when you later learn the fate of those who did go there, then you'll be grateful. Grateful to whom? To your own decision-making capability.
Or as noted by Neil Peart - if you choose not to decide, you still have made a choice.