A person who has the tendency to develop love psychosis if they fall in love and it doesn't go the way they want. Such as the significant other having 'mixed feelings' and confusing the fuck out of the love psycho (see unrequited love). Best case scenario, the other person lets the love psycho down in an easy and understandable way. Worst case scenario, the other person hurts the love psycho so badly that he turns from a psychotic into a psychopath and goes on a revenge-filled mass killing spree.
I TOLD that ice queen that I'm a love psycho and breaking my heart would be a BIG MISTAKE. But nooooo, she didn't listen! Now she's gonna PAY!