Genesis 17:17 Abraham laughs at God

When the Lord told Abraham that at the age is 99 he would have a child of his own born by Sarah, he laughed at God. Even though Abraham had asked God to give him a child and the Lord had specifically said to him that he would make his descendants more numerous than the sands and stars, Abraham still doubted Gods ability to deliver on his promise. How often are we like Abraham? How often do we ask God for something and then when He finally says ok we laugh and say "you're kidding right, there's no way". Who do we take God for, a fool? Do we not really believe when we hear His promises that if we ask we shall receive. When we pray, do we have a heart of unbelief, do we come before God with trepidation, not believing that through Him all things are possible? When God tells us that he has something for us do we deny it because we believe there is no way it could be possible? I know I have laughed at God because He has called me to do things that are outside of the realms of possibility in my mind. I think "there is no way I could do that", Well DUH! Of course I can't do it, I can do nothing apart from God who created me. I can't even breathe apart from Him. If He can keep my heart beating and my lungs breathing he can fulfill a promise or provide a way to a means, that part is easy for Him. How is it that i think i can do anything in my own strength? When He wakes me up every morning I do not question how he did it or why, I simply praise Him for another day. Our first response to God should never be laughter or doubt. The gracious kindness of the Lord is the only reason He hears my laughter and doubt and still says "just wait and see".