Something like that recently happened to me as a matter of fact. At the time I wasn't sure how to feel about it and I was just shocked by how much of an asshole this particular person was being to me. Later though, I was able to see that he had actually done me a huge favor. It works out that way sometimes, but it can and does go the other way too. When that happens it's not as much fun and it is very aggravating to have to deal with in a society that frowns on physical violence and revenge. Taking away the two best ways to respond when someone fucks up your day or worse yet your entire life really limits your options. You're essentially only left with bitching and whining to everyone who will listen or even worse resorting to pouring out endless streams of tears in blind fits of alternating states of rage and hopelessness.
Life is hard enough already all by itself without letting some asshole keep you from pursuing all that even matters in this life, your happiness. You can't change people or make them stop sucking because people just suck. I suck and you do too so stop worrying about it so much. Deal with the idiot in your way at the moment and then move on head held high and go out and be an asshole to someone yourself in pursuit of whatever it may be that you want.