“The word sadness (الحزن) does not appear in the Quran except in the form of forbidding it (ولا تهنو ولاتحزنوا) or in the form of negating it (فلاخوف عليهم ولا هم يحزنون).
The reason for this is because there is no benefit for having sadness in the heart. The most beloved thing to Shaytan is to make the believing slave sad by taking him off track.
The Prophet (peace be upon him) sought refuge in Allah from sadness (اللهم إني أعوذ بك من الهم والحزن) (in a Du’a). Sadness weakens the heart and diminishes determination and wanting to go forward. And there is nothing more beloved to Shaytan than sadness of a believer.
For this reason, be happy, optimistic and think good about Allah. Have trust in what Allah is able to do and depend on Him. You will find happiness and pleasure in all situations.
Don’t ruin your happiness with worry, and don’t ruin your mind with pessimism. Don’t ruin your success with deception and don’t ruin the optimism of others by destroying it. Don’t ruin your day by looking back at yesterday.
If you think about your situation, you will find that Allah has given you things without asking, so have trust in Allah that He doesn’t prevent anything you want except there is goodness for you.
You could be sleeping and the doors of the heavens are being opened with dua’as (supplications) being made on your behalf, subhan’Allah (Glory be to God) perhaps from someone poor whom you helped, or someone sad whom you brought joy, or someone passing by and you smiled to him, or someone in distraught and you removed it…so don’t ever underestimate any good deeds.
One of the righteous predecessors said: I make dua’a (supplication) to Allah for something I want, and if He gives it to me then I’m happy once and if He doesn’t give it to me then I’m happy ten times because the first was my choice and the second was Allah’s choice.” Ibn al Qayyim al Jawziyyah (may Allah have mercy on him)- poeticislam- tumblr