The writer records in Psalm 91 a prophecy of the wrath of God and what will happen to believers.
They understood this promise from the Lord concerning believers during the wrath of God.
"He will cover you with his feathers."

Jesus promised the same thing.
Mat 23:37
"Jerusalem, Jerusalem, you kill the prophets and stone to death those sent to you! How often I wanted to gather your children together the way a hen gathers her chicks under her wings! But you were not willing!

David offers this admonition.
“He wore cursing as his garment; it entered into his body like water, into his bones like oil.”
Cursing and related sins come easily and freely. Cursing becomes familiar the more we use it. It slips out at inappropriate times. It’s “usage familiarity”.

Compare “cursing as his garment” with our “garments of salvation”. (Isa 61:10)

May we be reminded of our “garments of salvation” when “usage familiarity” causes cursing to slip out. Remember we can't "unsay" anything.