Swearing to keep it casual.

No, this isn't going to be a manifesto on the prevalence of F Bomb dropping in polite society, of which I am a fan by the way; today's post was inspired by a conversation I had with my friend Carla last night.  Several months ago, she went out on a few dates with a guy, began to have feelings for him, then cooled off when she suspected he might have been lying to her about seeing other women, amongst other things.  She told him it was over, then spent the next couple of months being bombarded with text messages.  After bumping into him recently, he explained his situation quite plausibly and she decided to give it another try.  Although he hasn't stated it outright, Carla knows he wants to keep things fairly casual, and she says she is okay with this, but I know her.  Having a 'Special Friend' isn't going to satisfy her for long because she is a very moral woman with a lot of love to give the right person.  Personally, I don't have a problem with it; I've enjoyed no strings attached relationships in the past and can't swear that I won't again (with a surface dwelling guy this time), but my question is this: can a certified, ticket-holding commitment fan train herself to enjoy something more casual?  Obviously, for reasons I don't need to go into here, an ongoing fling can be a blast, but if you're the sort of person who has a blueprint for the future that involves growing old with someone, how long will it be before want turns into need?  My regular readers will know that, when it comes to my own romantic future, I'm a big fan of leaving things in the hands of Madame Serendipity.  If I find someone I can happily see myself legally bound to for eternity, great; if it turns out I'd prefer that he kept his shoes under his own bed, that's cool too.  But I do worry about Carla.  I've told her just to do what feels right, because all to often we're so busy playing monkey in the middle between our head and our heart that our gut is left sidelined, excluded from the game.