A brother Christian who once said to me, "You know, I've gotten to the point where all I care about is God's grace." He explained that he's in a Bible study with a Messianic Rabbi, and every time he gets tied up in some detail or point, the rabbi "hits me with God's grace again."
I suspect that the rabbi in question is emphasizing ADONAI's grace so much to try to avoid the period of legalism that so many Messianics go through as we discover a zeal for the Torah. Even so, the student in this case has gotten a bit unbalanced on the other side; he even once said to me, "Well, doesn't it say, let's sin all the more so that grace may abound?" No! Just the opposite (see Rom. 6:1-2)!
You know what grace is? Grace is sinning, going to our Father, confessing it, and having Him say to us, "You're forgiven; go and sin no more, My child." And when we stumble again and commit the same sin, and confess it, He says, "You're forgiven; go and sin no more, My child." And when we sin for the 491st time that day in the same way, our Father still says, "You're forgiven; go and sin no more, My child."
Grace is the pardon from sin, not the pardon to sin. Grace is a Father who accepts us as we are, in all of our sin and uncleaness, but loves us too much to let us stay that way. Grace is a Father who disciplines us (and yes, His discipline is often exceedingly painful), but who never rejects us. The Father may take us to the woodshed and take off His belt, but He always welcomes us back into the house with a hug.
That's not an easy grace. It's a very hard grace, sometimes--but it's a transforming grace.
It's very easy for a Messianic to get frustrated with a Sunday Christian. But if we, knowing the requirements of God's Torah, still stumble on the road and even wander astray from it from time to time, have been shown and continue to be shown so great a grace in our Messiah Yeshua, then we need to be just as quick to show that grace to our brethren.