Men feel lust when they have not felt penile orgasm.
Lust is both a behavior and an emotion. The behavior is about seeking the positive of penile orgasm. The emotion is a negative mental effect that coerces men until they feel penile orgasm.
Lust works like hunger.
If you don't eat, you feel hunger. Similarly, if men don't feel penile orgasm, they feel lust. The longer it has been since you've eaten, the stronger hunger becomes. Similarly, the longer it has been since a man has felt penile orgasm, the stronger the negative effect of lust becomes.
Hunger, loneliness, lust and boredom all function in the same manner.
If you don't do or feel enough of the left column above, then you begin to feel the right column. And the longer it has been since you have done or felt the left column, the stronger the right column becomes. The right column stops when you do or feel the left column again.
Women do not feel lust.
Although women do feel sexual pleasure like men, they do not feel lust. It's one of the reasons women masturbate less than men. Women just masturbate to enjoy sexual pleasure. Men also masturbate to stop feeling lust.
Relationships would improve if the lust gender difference was understood.
Men and women mistakenly believe the other sex feels the same emotions as they do. Men assume that women feel lust. And women assume that men do not feel lust. As a result, problems occur. Men do not understand why women do not want to have more sex. "Doesn't she feel lust as well?!" And women do not understand why men want sex so much. "Why does he keep pestering me for sex?!"
Simply understanding the lust gender difference would help. Men would be more understanding if their women don't want to have sex - because they don't feel lust. And women would be more willing to have sex with their man - because he's not greedy, he has a biological need.
For more about emotions, visit: Happiness Dissected