Now that we are saved by grace, and not by the keeping of the law, which we were never able to keep anyway - we still are unable to keep the law. Thank the LORD that we are saved by grace and kept by grace. All our attempts at keeping the law were self righteous, like a Pharisee, even when we keep them on the outside, we still have a perverse relationship to the law on the inside.
The only one who ever perfectly kept the law is the same one whose law it is, the LORD. The law is a picture of the true nature of the LORD, perfectly holy, righteous, merciful, just, gracious, showing us his attributes - his law reveals to us who he really is. No man has ever been able to live up to that law, and that law has condemned all of us of coming short, and deserving of its consequences. The LORD himself, who gave the law, came in human flesh, which we remember this time of the year. When the LORD was here in the flesh he only did that which the LORD does, he was perfect, holy, righteous, merciful, and lived the law, never breaking the law, because he couldn't. He wasn't "trying" to keep the law, i.e. this one & that one & that one, etc. He was who he always is, and his law is a picture of that.
Now that we are saved, he has given to us his Holy Ghost - the same God who gave the law. When we are filled with the Holy Ghost, or when we yield to the Holy Ghost, then he his doing in us that which he always does, he does right. He can only be holy, and he only and always lives the law by nature, because it is a picture of his perfect attributes. He doesn't "try" to keep the law, it is all he does, he cannot break the law.
So if we mortify our members and yield to him, then he will do that which is right in us. Any other combo effect, has our old nature "trying" to keep the law, but driven by self righteousness, like Cain. All attempts of ours to keep the law is based in pride and will fail because it is perverse like our fallen old nature. We never need to "try" to keep the law, as that would be for our glory.
No, the only way is through humility, first admitting that we cannot, nor ever can, attain the law's righteousness. Secondly by submitting and yielding to the LORD, then he, and he alone, and not us, is the one who is doing that which is right. And since the law is really a picture of who he is, and since he is the one doing right, then by default, and not by purpose of our wills, we will be keeping the law.
I have a number of friends who are part of the SDA, and they would go insane reading this, because their ultimate heart's desire is to go the way of Cain, to be law-keepers by the sheer power of their own might and will. They desire the self righteousness and self glorification that comes at the end of the way of Cain.