Why then does God so strictly enjoin the Ten Commandments upon us, since in this life no one can keep them?

Heidelberg Catechism

Question 115. Why then does God so strictly enjoin the Ten Commandments upon us, since in this life no one can keep them?

Answer. First, that as long as we live we may learn more and more to know our sinful nature,[1] and so the more earnestly seek forgiveness of sins and righteousness in Christ;[2] second, that without ceasing we diligently ask God for the grace of the Holy Spirit, that we be renewed more and more after the image of God, until we attain the goal of perfection after this life.[3]

[1] Ps 32:5; 1 Jn 1:9;
[2] Rom 3:19-26, 7:7, 24-25;
[3] Ps 51:12; Mt 5:6; 1 Cor 9:24-25; Php 3:12-14; 1 Jn 3:1-3