Mistakes happen, that's life.
Misfortunes happen, that's also sometimes life.
Whether something is a fault of your own or one that you just perceive to be, self-blame is an important thing to give up if you want to live out a relationship to its fullest potential.
Remember that communication needs to be at the core of every aspect of a relationship. If you made a mistake or believe you're at fault for something, voice any doubts or concerns to your partner and tackle the issue head on with discussion.