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there are no wrong or right decisions. disappointment only comes from when your estimated outcome for this decision doesn't match reality. but you never know what were odds for estimated outcome of another decision to match reality it created. so you never can decide, whether you made right or wrong decision, you only can judge on how you feel about your expectations not being in line with what happens around you.
it is very hard not to expect something, as a human being you tend to estimate outcomes for your actions, you tend to think, that you are able to do something that will result in something. but that is not like this. if you think that your decisions brought you up to the point where you are now, do not forget all of the millions and millions of possible little triggers that could have changed your life, drastically, this little tiny "turns" and "switches" absolutely do not  depend on you. human mind and human body are so fragile, whenever i think of all the possibilities for them to get destroyed, just in a blink of an eye, i don't think it is logical to think of oneself as master of one's life. if you're lucky enough to be whenever you are now, most probably you were lucky enough to avoid all those pitfalls that are always out there, the ones you never though of, not the ones you avoided by making some of your decisions on the way. if you're not lucky enough, do not blame it on yourself for making wrong decisions once in your life, just because they do not matter. as long as you're alive, you are alive, and yes, whether you made some decision in the past or didn't doesn't mean you would be in better or worse situation right now. if you're not alive, well, you possible would not be reading this of even trying to think of life in the same way as you did in human body. 

all in all, i developed this image of life in my mind, where we are just floating through reality, though empty space with infinite small things around us,  little strawberries, like in video games. we only float in one direction but can collect some strawberries on the way, when we pick up one, we miss out all the others which where around us at this particular moment. but the aim of the game is not to collect most amount of strawberries, or all of them, or the good ones (because they all are the same).
this little things are only there to make you feel you're doing something on the way, to create illusion that you collect something, that you own something. choice is up to you, you're out there in this space, you can either start playing the game, try to collect more of the strawberries, or pick only ones that you like, or pick non of them, just float through. as long as you're feeling happy with the process, traveling through space is good.