Arise, O God! Plead your own cause.
Remember how the foolish man
mocks you all day long.

“Remember.” This is the idiomatic or “pregnant” sense of “remember,” meaning remember, pay attention, and do something about the situation. “Do not forget” in Psalm 74:23 has the same meaning.
[For more on the idiomatic sense of remember, see commentary on Luke 23:42.]