God never intended for us to be left to pray on our own. God never changes His purpose, but He often does purpose a change.

A man may be carried on in a constant course of mortification all his days; and yet perhaps never enjoy a good day of peace and consolation.

I have known some good men who have been so addicted to their study, that they have thought the last day of the week sufficient to prepare for their ministry, though they employ all the rest of the week in other studies. But your business is to trade with your spiritual abilities. ... A man may preach a very good sermon, who is otherwise himself; but he will never make a good minister of Jesus Christ, whose mind and heart are not always in the work. Spiritual gifts will require continual ruminating on the things of the Gospel in our minds.

By faith ponder on this, that though thou art no way able in or by thyself to get the conquest over thy distemper, though thou art even weary of contending, and art utterly ready to faint, yet that there is enough in Jesus Christ to yield thee relief.

Not to be daily mortifying sin, is to sin against the goodness, kindness, wisdom, grace, and love of God, who hath furnished us with a principle of doing it.

the whole Pelagian poison of free-will ... a clear exaltation of the old idol free-will into the throne of God ... That the decaying estate of Christianity have invented.

Though we are commanded to 'wash ourselves', to 'cleanse ourselves from sins', to 'purge ourselves from all our iniquities', yet to imagine that we can do these things by our own efforts is to trample on the cross and grace of Jesus Christ. Whatever God works in us by his grace, he commands us to do as our duty. God works all in us and by us.