It's not convoluted at all. =) First, I want to let you know that marriage and family therapists are not restricted to working with couples and families. They can work with individuals of all ages. Furthermore, we don't just deal with relationship issues - we can help with any kind of mental health issue (so long as it is within our scope of practice, of course - if we don't know enough about something, we refer to someone who has more knowledge of the issue).
I think a certain degree of attachment is common, but you learn how to handle that during basic training at school. No, I don't think I will struggle with maintaining professional boundaries, but yes, I'm sure I will be sad to terminate therapy with some (if not most) of my clients in the future. We're human, so of course we're going to relate to their stories and feel a great deal of empathy - if we don't, then we shouldn't be in the field (that's what research is for)!