But, to enjoy these gifts, to be able to use them, the people needed instructions. And God had provided the necessary instructions for them. Now it's up to the people to follow those instructions.
Scholars tell us that our version of the book of Deuteronomy is the result of editing after the Babylonian exile. In their opportunity to start over, they could reflect on their ancestors' return to the land after their escape from Egypt--and on what had gone wrong for them--and, consequently, on how to do it right this time.
Praying the words of Psalm 25 is admitting that we have not done what we should have done. and, despite that, we can turn to the Lord for help. We ask for instruction as to what we should be doing, how we can now follow God's ways. We can do this because God is merciful.