The worst thing you can do is lead a girl on. Don't lie to her, don't make her think you're feeling something you're not. She won't forget the little things you did for her. She won't move on like you did. You'll be the only thing on her mind. She'll dream about you. Memories will KILL her. Don't make her wait for you if you have no intention of coming back. Just remember when you're talking to other girls; she'll be listening to the songs you dedicated to her whilst looking through your pictures crying. Don't promise her something that you can't keep. Don't ever promise her 'Forever' because like and idiot, she'll believe it .