You have to decide if you are in for the art or for the rush. If bombing really makes you feel better and you crave that adrenaline, then you should acknowledge that what you do is vandalism and it's not meant to be pretty (of course, you can make it "beautiful" to fellow writers' eyes).
But if you're into the artistic aspect of graff and you're uncomfortable with bombing and vandalism, then you should practice pieces and try to dismiss desire to go out to bomb. That's really up to you.
Personally, since i love bombing i tend to value quantity over quality, and i don't care if my shit doesn't look that good if i have hundreds of throws running in the city.
Basically, you have to do what gives you pleasure and, since there are no rules for graff, you can do the fuck you want. If it doesn't make you feel good, you're doing it wrong.