I have given good reasons to break up a relationship but I find it worthy to also have reasons why we should not break up. Some immature people can want to break a relationship because of pretty things like;
Trying to Make Him Mad
Or you're just trying to make him jealous, or to make him like you more. That's just a silly game that suggests you're not mature enough even to have a boyfriend. If you've got something to say to him, come out and say it - don't try to trick him by doing something you'll probably regret later.
You Got Into a Fight
Fighting part is of dating. Verbal fighting, that is. If it gets physical, get help. If you can get through the argument calmly and reach a solution that you can both live with, then it's a reason to stay together, not to break up.
Someone Else Wants You to Break Up
If you're feeling pressure to break up with your girlfriend, talk to her about it - and if you're getting bullied, get help from an adult. But don't let anyone get their way just because they're being a jerk.
You Have a Little Crush on Someone Else
If you've just got a little crush, and you haven't had it for very long, wait it out and see if it develops into a big crush. There's a good chance it might fade away, and you'll be glad you didn't do anything drastic.
You like Different Stuff Than He Does
You shouldn't spend every waking minute with your sweetie. The fact that you have different interests and want to spend your day doing different activities is a good thing, not a bad thing. Quit panicking about your time spent apart, and use it as an excuse to hang out with your friends more.
Never destroy your good relationships because of the pretty things above.