When do we need to hear this reminder? What prompts us to remember to give it?
Do we have to be living in bad times to be able to appreciate good ones?
Whom do we trust enough to receive comfort from what they tell us?
The original psalm may have been helpful to people living during the Babylonian Exile. They were dislocated, their king had been ousted, but they could hear reassurance that the Lord was still in charge, and the outcome for them was going to be all right.
And knowing this, believing this means telling what we know and believe:
Happy are the people who know you. They exult in your name all day long, and extol your righteousness (89:16).