Ibnul Qayyim رحمه
الله said
the word (الحزن) –
(sadness) does not appear in the Qur'aan except in the form of forbidding it
(ولا تهنو ولاتحزنوا)
or in the form of negating it
(فلاخوف عليهم
ولا هم يحزنون).
And the reason for this is because there is no
benefit for having sadness in the heart. The most beloved thing to Shaitan is
to make the believing slave sad by taking him off track.
The Prophet (ﷺ) sought
refuge in Allaah (سبحانه وتعالى) from
sadness
(اللهم إني أعوذ بك من الهم
والحزن)
Ibnul Qayyim رحمه الله said: "Sadness weakens the heart and diminishes
determination and wanting to go forward. And there is nothing more beloved to
the Shaitan than the sadness of a believer."
For this reason, be happy, optimistic and think
good about Allaah (سبحانه وتعالى). Have trust in what Allaah (سبحانه وتعالى) is
able to do and depend on Him. You will find happiness and pleasure in all
situations.