I wouldn't say it is bad. If you are at point where you need to get your emotions out, then its fine. If you sit home all day long and listen to sad love songs and do nothing else, then yes it is bad and not good for you. You will drive yourself into depression. As time goes on and you heal, you will still hear songs that remind you of that other person. The thing is with time you will be able to smile thinking of the good memories.