Perfection

"Each time you fall, He'll pick you up. He knows your own efforts are never going to bring you anywhere near perfection." -CS Lewis

Why do I expect myself to be perfect when He doesn't? I can make Him proud but do I ever disappoint Him? This gives me something to think of. He knows I'll never be perfect. He delights to see me walking in truth... When He looks at me He sees Christ... So again I have to ask, is it possible to disappoint Him? Are there any New Testament references to such? I know there is a verse that talks about being perfect like Christ but what about disappointing like the Israelites did in the Old Testament? I suppose I'll have to just read it straight through and see!