Blessing, in this psalm, is not based on prosperity, appearance, or success. It is tied to a spiritual relationship that requires forgiveness to yield blessing. The Psalm begins with blessed. That word means that we have divine favor stamped on our life. Like the Sermon on the Mount, this Psalm begins with a beatitude.
Word is barak, to be favored with some special benefit.
The Hebrew word is also in the plural, so that this literally means, O the blessednesses of . . . Many are the blessings of God that begin with forgiveness. That assumes that we know we have sinned, that we cannot please God in our own strength, and that we look to God to love us based on some Substitute. That is a lot of theology, if you think about it. At least three times, the same concept is restated in 1-2a.