I think what I mean is that I'm poly. By nature, at least.
I have two kinds of friends: ones I love and ones I like.
The friends I love I love with all my heart. I trust them with my soul, and I know they trust me with theirs. I will forgive the majority of trespasses and hope that they will help me through my screw-ups as well. These are friends, to me.
Friends I like are kinda casual friends. I don't spend much time with them, and I don't trust them with my soul. These are more like acquaintances. People I'm nice to. People who I like.
I have many more of the first kind of friend, and very few of the second kind. If I'm going to be friends with a person, I go all the way, unless they don't reciprocate. Even sometimes if they don't, I will still go all-out (like a crush, minus the sexual drive).
When I have a girlfriend (or wife, in this case), my sexual drive kinda just turns off to outsiders, because I think it the highest form of respect I can give her. That she's the only person I find attractive enough and the only person I want to have sex with. It makes her special, and I know many women desire this kind of connection.
Part of the reason I never try to start up sexual romantic relationships with some of the friends whom I love is because I cannot give them the amount of attention they would desire and deserve, so there's no point in trying, as it would only end up hurting my loves, including my primary love, and including myself. It would only result in pain and compromise all around. One person is too much already, and the fact that I manage to pull it off and leave the two of us feeling fulfilled (in a mono relationship) is part of what keeps me going.
Also, if I opened myself up to loving more than one person romantically, then I couldn't say things like "you're the special-est (not a doctor)" or "you're the best in the world," because that would be showing a preference for one over the other...and I kind of like saying things like that, and I know my wife loves hearing them. I'm pretty sure if she heard me say them to somebody else and mean it, she would be hurt.
So anyway, that's me. That's the reasoning behind my reasoning.
I am poly, by nature, I just feel a lot better when I am involved in a romantic sexual relationship with one person than when I am involved with more than one.
A loophole for me, that seems to keep me from feeling stretched and/or hurt by my own sexual actions is groupsex with multiple people I love. I have done this on a couple of occasions with girlfriends past, and we all seemed to get along okay in it. I never realised my motivations behind it until recently, as back then, I just thought of us as silly deviant teenagers having fun in our fort in the woods (because that's where it happened -- multiple times. I went to a boarding school in the Northwoods of Wisconsin, bordering on the Sylvania Wilderness.).
But for some reason, if/when I try having sex with somebody else I love, and I'm alone with just that person, I get wrapped up in a self-destructive loop of guilt afterwards, so I just don't do it. I worry that my primary will be hurt by it, no matter what she may say, because I don't trust words. Words are easy to manipulate to hide feelings. Very easy. As proof, my wife and I have been doing this for months, trying to make one another (and probably most of all ourselves) believe that we were okay, when we really weren't (for reasons other than poly -- this is a whole different bookshelf of stories, none of which shall be read here). Rest assured that our communication problems are being addressed, so feel no need to remind me how unhealthy the behaviour of lying to one another (and ourselves) about our true emotions is. We know. We're working through it.
So to clarify: I love everyone. I could start up a romantic relationship with any one of my friends (or try -- many wouldn't be open to the idea because I have a wife), but I just don't. I feel attracted to many of them, but I don't act on that attraction, because I only end up hurting myself, if not that friend, by not being able to create an exclusive relationship with that person, nor focus enough energy and time on them to make us both feel fulfilled. So I don't try, and just focus all my time and energy on my primary relationship (and don't feel fulfilled, but that's because our schedules really don't match up).