It doesn't matter how often you have a wet dream (nightfall).Many times boys/men discharge the semen during sleep (nightfall). This discharge is invariably accompanied by a sexual dream. It is a normal, natural and uncontrollable response to sexual tension that gets built up within the body. There is no reason to be worried, frightened or feel guilty about a wet dream. It happens with all men and is not a disease. It is completely harmless and has no ill effects on one's health or manhood.