Personally, I think it would be selfish to ask someone to stay in a marriage that made that made them unhappy, especially for the sake of the spouse/family. If you are unhappy being in a relationship with someone, how could you want to sleep in a bed with that person, have sex, wake up looking at their face, share meals together, go to family functions together, etc. It would be living a lie, and it would require closing off a part of yourself just so you could make it through the day.

I was in a 5 1/2 year domestic partnership and I became very unhappy beginning in year 3. However, I felt that because I made a commitment, I had to stick it out. So for 3 years, I was absolutely miserable. It got to the point that the sight of her face or the touch of her hand made me sick to my stomach. I lost a piece of who I was because I had to turn my "self" off just to tolerate being in the relationship. I had to turn off the part of myself that was screaming, dying to get out, and wanting to be free. I felt I was allowing myself to be constantly violated because I was allowing her to touch me, sleep in bed with me, etc., even though it felt disgusting and wrong. It got to the point that I remember telling my T at the time "I feel dead inside. I can't remember the last time I felt anything. I can't remember the last time I was happy, even for a second." Finally, I realized that having a "self" was worth more than the commitment I made to her-- and I overcame my fear of leaving-- and it was the best decision I ever made. It was a hard decision to make, though, because she didn't want the relationship to end. She wanted me to stay, even though she knew I was miserable. (I believe that is what was selfish; she knew being with her was killing me inside, but she put herself above me, all the while claiming she loved me-- if she really had loved me, she would have let me go). But, at some point, I decided I had the right to listen to myself; that I was allowed to matter! Now, 3 years later, I'm in love with the "right" person and I'm happy. I'm not just "living to live"; I'm like "can't stop smiling" happy-- in fact, just yesterday, my and my current GF had the most incredible Valentine's Day of my life. Now, I wish that I had left my ex-partner 3 years earlier, so that I wouldn't have undergone the trauma I went though as a result of the relationship. Because, honestly, there are times when it still affects me now-- but the only thing worse than having stayed with her as long as I did would have been staying with her one more day. Okay, that's probably a longer response than you were looking for, but it's what came up for me when I read your quesiton.