This psalm deals with young David being “captured” by the Philistines in the city of Gath — this according to the psalm’s heading. David had run away from King Saul, who was trying to kill the young rival for his throne; and had taken refuge with these “Cretans” who worshiped other gods.
“In God I have put my trust,” David the refugee says twice, early and late in this psalm. “I will not be afraid. What can man do to me?” Well, if what David himself did to his rivals means anything, then the answer to his question is, “A lot,” and much of it was barbaric, even to his own people.
“Vows made to You are binding upon me,” young David prays to YHWH. I guess that changed after he left Gath, returned to Jerusalem, and became king of Israel. I guess “Thou Shalt Nots” don’t apply to kings. After all, they aren’t really vows, as such; they’re rules made to be broken.