Pathological jealousy is when these feelings become clinical it's also sometimes known as delusional disorder. It occurs when people have repetitive ideas that their romantic partner is cheating on them leading to increasingly possessive behavior. The only way to overcome this disorder is to become comfortable with the idea that you know yes your partner might be cheating on you even if there is no evidence. But then again we are talking about a disordered version of jealousy so for the average Joe in their 20s or whatever age you might be jealousy can be reduced.