all of the above...
...plus, I believe that if a relationship isn't working for one person, then the relationship isn't working for both, even if one half isn't up to speed with that yet. I would not want to be with someone who was with me out of pity or because they decided that the other things that were going on in my life were too much for me to handle, and however painful catching up with them on their feelings about the relationship was, I'd far rather they were up front and ended it than drew it out.
I have stayed with someone out of guilt about how my leaving them would affect them. Or at least that is what I told myself, actually when I delved, my reasons were more selfish and this was my excuse (I couldn't do this delving at the time, I didn't have the emotional distance to explore it in that way). I am not saying this is the same for you, just my experience.
