Ok, this is really bothering.
I was lucid last night and decided to have sex with someone from my class. I had a full control over my dream, and created that guy and wanted to sleep with him but he run away!!!
I mean, how is that possible? Is that even legal for him to run away from me, when I have him under my control ? hehe
did you have any doubts in your mind that it wasnt going to work out? like you had a crush on him for ages but you wouldnt say anything to him for fear of rejection or something. if that was the case, then maybe that crossed over into your dream as well.
other than that i dont really know
Well, he has a girlfriend in my waking life, and I saw her in my dream too … but I thought “well its a dream, so what does it matter” and went towards him …
I guess that should answer it, but on the other hand, it is MY dream! hehe … like my rules should apply… 
The way I see it, if you have a lucid dream, you know what you’re doing. You control your own actions (if not that of the other people in the dream). Even though you know it’s only a dream, what does your choice of action say about you as a person if you decide to do something like trying to make a guy cheat on his girlfriend? I just don’t think it’s right, which is why I think it’s a very positive thing that he ran away! It shows that some part of you knows it’s wrong to force others to do what you want.
If you see him again in your next lucid dream, instead of trying to make him do exactly what you want, why don’t you ask him something and give him a chance to make up his own mind? He might not be real, but he’s part of your sleeping brain. You might as well be kind to it!
The thing is, in my real life, I would never go for someone who has a girlfriend. Its like I have no interest in destroying someone elses relationship or getting between two people etc. Does not mean that I dont think that someone is sexy though. Yet I would never (I know = never say never) go for someone with a girlfriend.
I suppose you are right Stormthunder, maybe my subconces made him run away, simply because it knew my real self. I guess next time I just have to imagine someone who does not have a Gfriend! 
I just thought it was really ironical when I woke up. Even kinda philosophical, being dumped by my own dream character hehe.
(it did not bring much self confidence to my waking life I have to say hehe).
if they run away you just run faster LOL
He must not have liked you… 
It’s all a matter of trusting yourself with no doubts. Not that I encourage these acts in dreams, but the same goes for anything you’re trying to control.
just materialise a potion to make him like you and put it in his drink or something like that
Why, are there rules? 
You probably don’t feel that the guy would actually do anything love–wise with you, so it’s a self–esteem issue. Tell yourself next time he will sleep with you and he probably will. 
It’s as simple as that.
Try another time. It didn’t work on the first time yet it may work on the second.