SADNESS IN QURAN
We become sad at times whereas sadness is never mentioned in Quran except in forbidding way or negating way. We feel depressed at times. You hear most of the time so and so is in depression. A Muslim can be sad as it is not mentioned in Quran. Smiling gets us many good deeds. Allah says always be smiling when you meet or depart. Sadness weekens the heart. Never allow sadness to come near us. I heard many people saying their supplications were never answered by Allah so he is sad. You know what is Hadith if the supplication is answered, you are happy one time, if the supplication is not answered you must be happy 10 times as this may be for your good.
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A Muslim must avoid sadness & depression. If you remain always smiling, you cannot be sad or depressed.