If you're unhappy with a relationship (friend, spouse, significant other, boss, fellow employee, sibling, etc), don't think that it's the other person's fault you're unhappy. You can make the most of a situation from an internal perspective no matter what's going on externally. Remember how the POWs in World War II survived in their tiny crowded rooms - they did it with their mental attitude and thoughts. They were able to project themselves away from their present and into the future, or at least into a more pleasant part of their memory.
You can do the same as the POWs - many of you may feel as if you're a prisoner of war in that relationship so this isn't that far off.
Instead of focusing on the things you don't like about the relationship or characteristics of the other person, focus on yourself and your contributions to the relationship. You can also do the "Book of Positive Aspects" where every day you write down at least 3 really good things about the other person. Don't even go to the negative aspects at all. It make take you awhile to come up with some things but do the simple little things so that you have something good to write. The point of this is to focus on good things about the other person if you have to go there at all. If you can just think about your own happiness (and you can't say you WOULD be happy if..... if they would change or if you were out of the relationship or if this or if that...."if"s are NOT allowed in this game.
Focus on where you can change or even better focus on what the Universe may be telling you. You attracted this relationship remember. I know you don't want to believe that but you did. So take a look at it and see what is going on in your head and your emotions that is attracting these things you don't like or want. Look at your beliefs and see if you can track it down that way. For example, do you believe that all men (or women) cheat on their partner? Was that your experience in your family of origin perhaps? If so, that would follow that you'd developed that belief. Maybe you believe that you don't deserve to be happy. If so, you'd naturally attract situations where you wouldn't be happy. Maybe you think that work should be hard and you should be unhappy at work (struggle). So, you'd attract a boss who would make you work hard or you'd attract situations where you don't have enough staff or you have incompetent staff and you have to work hard to make up for that. Maybe you believe you're not good enough for a loving relationship or you don't deserve to be loved or aren't worthy of love. What do you think is going to be in your life if that's your belief? Yep, you got it....the exact circumstances you're trying to avoid.
Uncover your beliefs, do the Book of Positive Aspects and then see what happens in your life. Many times, your relationship changes for the good. Don't count on that though or that will defeat the purpose of this exercise. The purpose really is to help yourself feel better in your circumstances no matter what does or doesn't happen externally.
Think about it; try it.