Weakness should not keep us from duty.

“It should encourage us to duty that Christ will not quench the smoking flax, but blow on it till it flames. Some are loath to do good because they feel their hearts rebelling, and duties turn out badly. We should not avoid good actions because of the infirmities attending them. Christ looks more at the good in them which he means to cherish than the ill in them which he means to abolish. Though eating increases a disease, a sick man will still eat, so that nature may gain strength against the disease.
So, though sin cleaves to what we do, yet let us do it, since we have to deal with so good a Lord, and the more strife we meet with, the more acceptance we shall have. Christ loves to taste of the good fruits that come from us, even though they will always savor of our old nature.”

Richard Sibbes (1577-1635)