The Psalms are so rich in their repeating of things we need to know - God is so aware of that and He gives it to us.
"Give me understanding, that I may keep your law, and observe it with my whole heart."
I thought of understanding in a couple of ways...understanding of who I am (sinful, dead, broken) and who God is (Power, all, sustaining, merciful - I could go on). But, I think of my sinfulness this morning in light of the never ending mercies of God that are new every morning. How coming to Him is so refreshing - and wonder why I don't stay here all the time. But, again, His mercies are so receptive. They are receptive because of the finished work of Christ on the cross - who is for me for His glory.
So, in all that - give me understanding that I may observe/keep/protect/guard the perfect law that is in your Word, but not only keep it and guard it - but DO it with everything that is in me.
And as James Mac said this morning - I can't do it on my - but it is only Christ through me - that is something that Brad and JD already remind people of - DONE, Christ in me.