I've been born completely healthy, but when I was 19, I got a severe stroke, which has made me wheelchair-bound. Naturally, I am REALLY pissed off about my situation. I often feel the urge to take it out on other people, but since they aren't to blame for my situation, I know I don't have the right to do that. My question is: what right DOES my situation give me?

You need to learn how to take advantage of that wheelchair and develop a wheel chair based sense of humour, preferably at the expense of other people eg. go to a park and complain to a park ranger about there being too much grass and not enough wheelchair access. Also join a local wheelchair sports club, they make some people glad to be disabled