Of the characteristics of the believer is that he is always of cheerful countenance. Abdullah b. al-Ḥārith said, "I never saw anyone smile more than the Prophet (SAW)," and Jarīr b. Abdullah remarked, "I never saw the Prophet (SAW) except that he smiled when he saw me."And our Prophet (SAW) encouraged us to be charitable with our smiles, and said that every smile is counted as an act of worship that we shall be rewarded for. As well, the Prophet (SAW) would regularly laugh (although his laughter was always dignified and just a step more than a smile), and even crack jokes and pull pranks. So the believer is cheerful, and brings cheer to other people - in contrast to some religious folks who seem to think that scowling at people is somehow a mark of religiosity! Smile, it's Sunnah !
Yasir Qadhi