Praise awaits  you, O God, in Zion;
to you our vows will be fulfilled.
O you who hear prayer,
to you all men will come.
When we were overwhelmed by sins,
you forgave our transgressions.

God is a covenant keeping God to a people who are crooked and rebellious. The Psalmist is teaching that God is always consistent in sustaining creation and forgiving His covenant people. Even tho God is always faithful in upholding His word and covenant we cannot claim  that we fulfill our vows without atonement. The Psalmist is  teaching that all men live before this faithful God and they are required to come to Him for atonement. All men will come to Him in confession. Not only does God atone for our sins but just like He sustains the creation so He has chosen us in so that as He is faithful so we are faithful. If we were not faithful then there would be no unity and faithfulness in the nation.So we must have continuous atonement in order to sustain the unity of the nation.God had to chose us before the foundation of the world so that we would not become covenant breakers and destroy the nation.He chose weak and dependent people who are overwhelmed by their rebellious hearts and sustains us by His eternal covering of sin.Just like God sustains the creation on a daily basis so we can recite  this Psalm with confidence that God is sustaining us. We should know the God who is more ready to cover over our rebellion than to hold us to the perfect standard.