I suspect that you could try one thing differently - instead of manifesting yourself as being in love, just manifest him as being in love with you, needing you, etc. And even if they're in a relationship with someone else, relationships can fail or be broken all the time, or people cheat. I've encouraged and enjoyed the latter at least twice.
But yes, attachment to the result feeds doubt which defeats the entire purpose. And for all my potential lack of energy to use, I don't seem to particular dislike the sense of power or control. Its quite often that I get the specific desire but not my actual goal - an inevitable result on focusing, perhaps too much on the symbols rather than an end goal(I want XYZ girl, not a happy relationship!), but it still is rather a enjoyable ride.