All you have to do is read Scripture to know that from the beginning of Creation, people have used excuses to try to get out of having God use them in miraculous ways. Yet when they were finally willing to be used, God was still willing to use them. He has the power to accomplish what anyone would deem "impossible", and there's no limit to what He can do in us and through us for His Kingdom -- if we're willing to get rid of our excuses.