I would like to expand on atroyn's reply: Every choice you ever make is self-reinforcing.

If you choose to do the "right" thing or the "wrong" thing in any given moment, that will reinforce your tendency to either persevere or to give up, in the future.

So while some moments of decision may seem more important than others (with obvious / immediate consequences), these moments are in fact all supremely important.

Over time these decisions solidify into habits and character traits. Ultimately, they will determine your fate in life.