So my theory is this, I had already told you I believe that everything that happens is as a result of what we have thought and conditioned our mind to believe.
Am sure you’re thinking so what’s the relation between this statement and reverse psychology?
He will hate the idea that you find his friend more interesting!
Dont ignore him too much or else he may just lose interest in you.
Your Ex will think you are trying to manipulate him/her and this will push them further away from you (tsk tsk tsk).