I learned my lesson the hard way, and I will not repeat that again. 

When you RS someone who is in a relationship, they will think of you and not the person they are in a relationship with; but they won't be able to associate their horny feelings with you immediately and might seek it from other people (their partner). I suggest you do love visualization first, constantly, multiple times a day. Then when you get them back, do sexual influence. 

There was one point that I forgot to say about that I think is important, and that is, with any type of loa, anything you FOCUS on will eventually come into you reality, good or bad. So if you, for example, worry about the person falling into someone else's arms, then that will come into your experience, simply because you have sent out that particular vibration. On the other hand, if you don't focus on that kind ot thing, then the universe will respond accordingly and you will never have that unfortunate situation enter into your life. Actually that applies whether you are doing RS or not.