"Well, a girlfriend once told me never to fight with anybody you don't love"

This quote by Jack Nicholson is a reminder to reconsider before entering an argument with someone. It suggests that if you don't have strong sensations for the person, then it's not worth it to combat with them. It indicates that if you do not enjoy somebody, then it's not worth it to lose your energy and time on a fight. It also suggests that if you don't have strong feelings for somebody, then it's better to just walk away and not take part in a battle. This quote is a pointer to think prior to you act and to not let your emotions get the best of you. It's a suggestion to think about the consequences of your actions and to not let your feelings cloud your judgement. It's a tip to think twice before getting into an argument with someone you don't like.