Consider that it is...giving up your endeavors that will be your ruin. The woman of Canaan, in her great outcry to Christ for mercy (Matt. 15:22), had many a repulse. First, it is said, He answered her not a word; then His disciples desired that He would send her away that she might not trouble Him any more; whereon He gives a reason for not regarding her, or why He could justly pass her by; she was not an Israelite, unto whom He was sent; yet she gives not over, but pressing into His presence, cries out for mercy (v. 25). Being come to that issue, to try and draw out her faith to the utmost, which was His design from the beginning, He reckons her among dogs that were not to have children’s bread given unto them. Had she now at last given over upon this severe rebuke, she had never obtained mercy; but persisting in her request, she at last prevailed (verses 27,28).
It may be you have prayed, and cried, and resolved, and vowed, but all without success, as you suppose.....You know not at what time God will come in with His grace, and Christ will manifest His love to you as to the poor woman, after many a rebuke. It may be, after all, He will do it this day; and if not, He may do it another: do not despond. Take that word of Christ Himself for your encouragement (Prov. 8:34), "Blessed is the man that heareth me, watching daily at my gates, waiting at the posts of my doors." If you hear Him and wait, though you have not yet admission but are kept at the gates and posts of the doors, yet in the issue you shall be blessed."
~ John Owen