No relationship is perfect. There are some problems that can break a relationship. Here are relationship dealbreakers and knowing when it's time to call it quits:
1) Cheating. You heard it was a mistake. Once someone cheats they will do it again. The trust is gone and you can never gain it back.
2) Abuse. Weather it is; emotional, physical or verbally it is abuse. Once it starts it will only get worse. You can end up in the hospital or the relationship can end in tragedy. That's why once that hand is raised it is best to walk away.
3) Your significant other is checking out other girls in front of you. If his attention is on the hot waitress more than you, most likely he is thinking about other girls. If he acts single it's because he wants to be single. This behavior can lead to cheating. So quit while you are ahead.
If a relationship is more stressful than peaceful it is time to get out. Things will only get worse. Trust is needed in a relationship and relationships are supposed to be peaceful and give and take. Don't waste your time by staying with someone who won't put you first.