There's a joke that goes when a man gets married, his wife changes everything about him and then complains he's not the man she married.

While it isn't entirely true, the sentiment goes both ways. So if your significant other makes a romantic effort this Valentine's Day, give them some credit for trying instead of remembering all the ways they have let you down. 

A new Northwestern University survey/study says that the more you believe your partner is capable of change and perceive that he or she is trying to improve, the more secure and happy you will feel in your relationship. That is true even if you think your partner could still do more to be a better partner.

"Many of us tend to under appreciate our partner's efforts to improve the relationship, simply because we do not have enough faith in those attempts," said Chin Ming Hui, lead author and a fourth-year graduate student in the department of psychology at Northwestern. "When we see those efforts in a positive light, we can enjoy our relationship much more."

In this study, romantic couples were separated and asked to rate how much their partner was trying to improve his or her relationship-oriented characteristics, such as patience, understanding and being a good listener.

Three months later, the same couples were asked to rate their partner's current standing on these relationship-oriented characteristics and their overall feelings about the relationship. The results of the study showed that the more you think your partner is incapable of changing, the more your partner's sincere efforts fail to improve the relationship.

"If you don't believe that your partner is capable of changing his or her fundamental characteristics, even when he or she is working hard to try to improve your relationship, you can actually end up discounting these efforts," said Daniel C. Molden, senior author and an associate professor of psychology at Northwestern. 

The good news for those who are skeptical of a partner's ability to change: with self-awareness and effort, you can convince yourself that your partner's effort does matter and that your relationship can improve.

"A secret to building a happy relationship is to embrace the idea that your partner can change, to give him or her credit for making these types of efforts and to resist blaming him or her for not trying hard enough all of the time," Molden said.

This study was published in the Personality and Social Psychology Bulletin.