I have an interesting hypothesis on this topic:

Basically, everything that exists is a result of natural, physical laws. Any combination of these laws that are different from the ones we have yield a universe that simply falls apart, unable to sustain itself.

Now, why do you exist? Because of your parents; why do they exist? Because of theirs. And so on, all the way back to the big-bang.

Why do you like the things you like? With food, for instance, you don't have a choice what your tastebuds report to your brain. Why do your tastebuds report what they report? Because of your genetics; why are your genetics what they are? Because of your parents, and then theirs, all the way back to the big-bang.

What I am trying to say here is that the laws of physics are literally Fate. For you to have made a different decision is impossible, since that would have required a different big-bang made of different elements, ruled by different physical laws; for instance, if you were to "copy paste" the big-bang a million times, you'd get the exact same people making the exact same choices, every time.

I take solace in this fact; it alleviates regret, if only slightly.

But what do I know? Haha.