I don't think it's possible to want to breakup with someone you're in love with or feel happy to be with. Just because you have not been "fighting" or "arguing" doesn't mean you are meant to be together.
Too often what happens is people that are either bored in their relationship or no longer feeling happy will end up cheating. The first thing their mate will say to them is: "Why didn't you just tell me you wanted out?"
It's not necessary to go through a big drama filled nightmare in order to "justify" breaking up with someone. If you are unhappy or just plain want to date/see other people then that is enough of a reason to end the relationship.
It sure beats the hell out of getting caught cheating on them.