Thomas Boston, Works, 6:427:
Purposes without endeavours are but fair blossoms without fruit, which will never prove a penitent. If the lame man be cured, though not perfectly cured, he will rise and walk as he can. It is true, while here we can do nothing perfectly well; but the true penitent will endeavour to do all, and aim at no less than perfection. Hence said Paul, “I press toward the mark, for the prize of the high calling of God in Christ Jesus,” Phil. 3:14.
Source: http://www.puritanboard.com/f25/he-will-rise-walk-he-can-85328/, Comment #1