I have just separated from my husband of over twenty five years. I cannot say for him that he was perfect, but he was not horrible either. There was a lot of emotional and financial abuse over the years though, but also yes, him changing from very good father and a husband to a very passive one who was not very engaged. He is also kind of narcissistic, self centered and can be rude. I felt like he did not really respect me, appreciated me or loved me (although he was always saying "I love you" to me, but I do not think he really knows the meaning of the words). We did not communicate so well, we could not discuss things in a calm and productive way. Whenever I would bring a problem up, he would become defensive and eventually stop talking to me. Silent treatment was his method of "communication" and more and more I felt like we were stuck, like we were getting nowhere. I was feeling more and more unhappy to the point of feeling suffocated. He too wanted us to be intimate but I had no interest in sex for years. I did "make my self available" (god this sounds so awful) as much as I could though to avoid conflict and sulking and silent treatments, but I could not do that any more either.
Funny thing is, he was "shocked", did not think it was "that bad", when I finally told him that I wanted to separate. Even though over the months I had said many times that our marriage was in "crises", started counseling and offered him to go to couples counseling which he right away refused.
Anyway, he moved out one month ago and although I often feel anxious and sad and guilty, I know it was the right thing to do. It felt so good to tell him that I wanted to separate, to say it out loud, to feel like I am finally being true to myself, that I am finally validating my own feelings rather then pushing them down and away.
The thing is, you do not have to look for reasons, excuses. You do not have to justify your decision to anyone. Your needs and feelings are good enough reason to decide to move on. A relationship sometimes run its course and it is time to go separate ways.