It seems to me that we are part, that is our completed position in Christ, is part of His completed work. I cannot become more complete in Him. That is done. I forget that.
I begin to try to gain favor with what I do for the Lord. I know it sounds silly, but there is part of me that thinks that if I am consistent in Bible study, prayer, and other disciplines, somehow that makes me better, more complete. So I strive. I do not rest. I do what the writer of Hebrews is cautioning against. I set up some sort of system by which I can gain favor and go about busily failing at the system I set up. Talk about futile.
It seems to me that my personal worship of Christ would be better served to simply praise Him for what He has already accomplished in me. To rest in His completed work. To revel in His glory and linger long in His presence without trying to gain favor that He has already bestowed on me.
But I forget.