These are just a few quotes I live by, regarding keeping/maintaining good relationships:
Don’t play the “blame game”; nobody wins.
Just because you did not cause the problem, doesn’t alleviate you from any responsibility to solve the problem. All parties are still responsible.
Rather than focusing on what we can do to change our partner, focus instead on how we can change ourselves to bring out the best in our partner.
Don’t put the burden of “making you happy” on your partner. Make yourself happy!