With any relationship there comes a time when things stop being "perfect" and cracks begin to show. The reason for this isn't necessarily that the couple isn't a match for each other, but rather that the "real" personalities are beginning to show.

When out looking for a new partner, you don't usually show yourself warts and all. You present your best side hoping to attract the person of your dreams. You don't want them to see how untidy you are or your personal bad habits. You want to create the best impression possible. And so do they! Once the relationship settles and there's some security in it, the "perfect" masks begin to drop, and that's where the relationship starts to falter.

What you need to consider is what part of your girlfriend's flaws are you willing to accept, and which of them are unacceptable. We all have things that could be improved upon, and your girlfriend probably has some issues with your personality traits also, but there are some things that are usually non-negotiable and part of knowing when it's time to move on, is learning what your relationship-breaking issues are.

It's possible for someone to change, but saying they're going to change isn't the same as actually doing it. Even making a commitment to change is no deal if the commitment doesn't lead to action to back that up. Change will always require action of some kind or another, and you may find that once you see some improvement in the behavior you don't like, you can come to a compromise that makes you both happy about the issue.

Think about what it is about your girlfriend that has you considering that it may be time to move on. Have you talked to her about how you feel about the things she does that you don't like? What was her response? If she thinks that you should accept her as she is unconditionally, then you have to think about whether or not you can do that. Has she tried to make you change any of your habits to suit her? Does she accept you unconditionally or is this a double standard she is presenting? Has she said that she'll try to change but either hasn't tried, or tried and then reverted back to the old behavior?

If both of you are committed enough to each other and your relationship to work on the things that the other doesn't find acceptable, then your relationship has a chance--every couple will find themselves compromising at some point or other because that's part of the give and take of being two individuals in an equal partnership. However, if you can't accept her as she is without any reservation, or if she is expecting you to make changes that you aren't prepared to make, then it's time to move on.