"God's commandments is not too difficult, nor is it beyond your reach. The law is not among those things that the humble person does not bother with (Ps.131:1) or that even the wise find beyond their understanding (Prov. 30:18). It is not, therefore, impossibly idealistic, impracticable, unachievable. We have noticed eariler the balance achieved between ideal standards and eartly realities. The idea that God deliberately made the law so exacting that no body would ever be able to live by it belongs to a distorted theology that tries unnecessarily to gild the gospel by denigrating the law. The frequent claims by various psalmists to have lived according to God's law are neither exaggerated nor exceptional. They arise from the natural assumption that ordinary people can indeed live in a way that is broadly pleasing to God and faithful to God's law, and that they can do so as matter of joy and delight. This is neither self-righteousness nor a claim to sinless perfection, for the same psalmists are equally quick to confess their sin and failings, fully realizing that only the grace that could forgive and cleanse them would live wise enable them to live again in covenant obedience. Obedience to the law in the OT, as has been stressed repeatedly, was not the means of achieving salvation but the response to a salvation that was already experienced"
-pg 290 of Christopher Wright's commentary on Deuteronomy