It is reported by Sayyidina Abu Hurayrah RA that the Prophet said, "Laugh little for much laughter deadens the heart."
Sayyidina Abu Hurayrah RA has reported the Prophet as saying, "Avoid much laughter because much laughter deadens the heart."
Tirmizi Ibn Majah
Sayyidina Abu Hurayrah RA stated that once the Prophet met a group of his companions RA who were conversing together laughing. He remarked, "By him who has my life in his power, if you were to know what i knew then you would laugh little and weep much." He then went away from while they wept.
Allah sent a revelation to the Prophet , "O Muhammad, why did you cause my slaves to despair?" The Prophet returned to them and said to them, "Be happy, and compose yourselves. Try to perform good deeds."
These ahadith tell us that it is not good to laugh much. It takes away life from the heart meaning the fear of the Hereafter is no more felt by it and it does not ever think of death. The heart comes to neglect zikr (remberance of Allah ). To neglect zikr is to die, for it is zikr alone that fills the heart.