Tawheed is the key

From Umm Ahmad Bint ‘A´ishah that she said: My mother, may Allaah have mercy on her said to me:

“O Daughter, dont be happy about something that will vanish (i.e, enjoyments of the dunya)! and dont be depressed over someone leaving. Be happy for the sake of Allaah Azza wa jall (i.e, by worshipping Him, calling Him etc). be only depressed about falling from the eyes of Allaah azza wa jall (i.e by disobeying him with sins).”

A´ishah said: and i heard her saying: “stick to manners with Allaah azza wa jall inwardly and outwardly! for no one is bad in manners outwardly, but will be punished outwardly! and no one is bad in his manners inwardly but will be punished inwardly! and he who feels lonely alone, is because of he dont feel the good time with Allaah Ta’ala”

[from sifat as-Safwah, by Ibnul Jawzee]