Also try this experiment: on one occasion, actively pursue an opportunity "overheard with friends" - when that activity is complete, recount the entire experience and decide if there was truly something you could have lived without. On another occasion, actively turn down such an opportunity and pursue something in the meantime. If you can do this once, do it again, and you'll start to learn to balance the pursuit of such opportunities and likewise a restraint. As motivation: If you don't turn down an opportunity then you are missing out on this experiment!
For example:
-> I often start to preemptively regret my decision
Why do you regret your decision? Perhaps it's because there may be a more optimal decision? Why does the decision matter? Maybe you've had some failures in life and its time for an epic comeback, so you can't afford to lose. Why does it matter if you lose anyway? Maybe you feel that your friends/family will deem you worthless if you don't succeed?
If this is your train of thought, then the solution is simple: find better people to hang out with. [0]
[0] The solution isn't that trivial, but this actually would help if my example resonated more than it should've.