This first applies to me, then to everyone else.
I have heard many people give awesome supernatural testimonies. But seldom we can see a changed person. In fact I know people who can recite almost most of Bible without seeing,yet remain the same in being greedy for money, angry, envious and lustful.
How can it be that we know Christ for 30 years and yet we remain the same. In fact changing ourselves can never happen even if we try hard. It only happens when we allow him to work him our lives and surrender ourselves to his will.
Change in us is the sure testimony of the only living God. It is easy to memorize the scripture, attend all the mass meetings held, hear best of sermons, yet tough to bring a small change in us.
But remember, God makes all things possible.