“And I will make an everlasting covenant with them, that I will not turn away from them, from doing them good.” - Jeremiah 32.40
You remind me of their unworthiness. Yes, but observe that when he began to do them good they were as unworthy as they could possibly be. He began to do them good when they were "dead in trespasses and sins." He began to do them good when they were enemies, rebels, and under condemnation. When first the sinner feels the movement of divine love upon his heart, he is in no commendable state. In some cases the man is a drunkard, a swearer, a liar, or a profane person. In certain cases the man has been a persecutor like Manasseh or Saul. If God left off blessing us because he could see no good in us, why did he begin to do us good when we were without desire towards him? We were a mass of misery, a pit of wants, and a dunghill of sins when he began to do us good. Whatever we may be now, we are not otherwise than we were when first he revealed his love towards us. The same motive which led him to begin leads him to continue; and that motive is nothing but his grace.
(From a sermon in 1889)