As-Salaam alaikum,
Malik ibn Anas reported from Yahya ibn Sa'eed who quoted it from Sa'eed ibn al-Musayyab, who quoted it from Umar ibn al-Khattab, may Allah be pleased with them all, who reported that the Prophet, Sallallahu alaihi Wasallam, said : "Always remember the terminator of pleasures". So we asked, "What is the terminator of pleasures, Ya Rasulullah?" He replied : "It is death". (Hadith Sahih).

In another hadith, on the authority of Anas, may Allah be pleased with him, the Prophet, Sallallahu alaihi Wasallam, said : "Remember death recurrently because so doing wipes out sins and makes you disregard this worldly life".

So, if one is in distress, remembering death will alleviate his/her pain because it (death) is harder than any other misery. And if he is in a state of happiness and abundance, remembering death protects him/her from rolling in the pleadures of life and counting on it... as we must part with it one day.