I was originally friends with my Master. After a while we got to know each other and he respected me more than anyone (including those in my family).
I am a natural submissive (not sure if people can be or not but thats what it feels like to me.) I find it easy to please others than myself. Especially when it came to my Master.
So after we reached the level of boyfriend/girlfriend that's when I chose serve him, I wanted to make him happy because he makes me happy. So I feel that being submissive to him, makes both of us happy. Which to me is the main thing.
It's a deep bond we share and are happy. Even if we didn't enter the community, I'd still be his in all aspects.
(sorry if my thoughts are a little disjointed.)