If you're not doing it because you really care about something (health or ethical issues) then don't bother. Like other posters have said, we are designed to eat meat and nature is far crueler than we could ever be. Eating meat is a fact of life. If you don't eat that much meat anyway then you have nothing to worry about, forcing yourself entirely one way or the other is counterproductive.
If your girlfriend wants you to give up meat to satisfy her self conscience. Then what is she going to do for you?