No matter how much we try to be good we always seem to eventually fail - but those who are into God through Christ are seen as perfect from God's point of view - this is one of the mysteries that we can be perfect in Christ and strong through Him even when we are weak. In fact when we are weak we end up depending on Christ and allow Him to be strong for us - He wants us to depend on Him because when we depend on ourselves. We always seem to eventually fail.