I need to be more selfish

I need to stop caring about what other people think. Occasionally (ok, more like daily), I'll think about quitting my job and running away to do something else. When I seriously consider doing this, I start feeling this surge of guilt. I feel guilty that I would be letting other people down. People like my parents and even my boss. This bothers me because, why the hell should I be feeling guilty for wanting to do something else? Why do I care what these people think? Shouldn't my feelings come before anyone elses?