Oh, to Long!

You have seen a dog after a long run; how he stands with opened mouth panting for life and breath. Oh, that we had desires after God and divine things strong enough to make us thus open our mouth and pant! We may never have seen a stag in extremis, but I dare say David had. He had seen it in the fierce hunt, when it longed to have its smoking sides in the water brooks and to drink long draughts, and he said, “As the hart panteth after the water-brooks, so panteth my soul after thee, O God.” 

Nothing puts such energy into prayer as intense anguish of desire. Desire comes out of a sense of want; and in proportion as the necessity is overwhelming, the fervency of the desire will be vehement. My brethren, we have not, because, although we ask, we use a kind of asking which is as though we asked not.

An old Puritan says, “He that prays to God without fervor asks to be denied.” There is a way of asking for a thing in which the person to whom the request is made finds it very easy to decline the request, but persons in dire necessity understand how to put the case, so that only a very hard-hearted person could say “no.” They know how to place their petition in such a way that the request wins, not merely because of the rightness of the petition, but also because of the very style in which it is put. We must learn how to pray with strong crying and tears, for there are mercies which cannot be gained by any other mode of supplicating. 
From a sermon by Charles H. Spurgeon entitled "Opening The Mouth."