Once we get past the context of the times in which this psalm was written, its instruction becomes clear. In those days, idols of stone, wood, and metal fashioned into the form of an angel, man, beast, or half-man/half-beast were common. People worshipped before these figures and tried to conform their lives to what they thought its will was. The lesson is that a man can rise no higher or be no stronger than his idol. An idol—anything worshipped that is not the Creator God—is inadequate. It can do nothing to improve what the man is.
Compare this to those who allow their admiration for an athlete, entertainer, or politician to slide into idolatry. What are they worshipping? Just another frail and fallible human being. Conforming to their idol’s way may earn them notoriety within their peer group or community—it may even earn them a great deal of money. In this life, they could even become “greater” than their idol, but in the end, what and where are they? They are still just frail and fallible human beings just like the one they worshipped. Worshipping anything less than God does not enable us to rise above being merely human.