Well ok, it does not matter that one has not lived according to Jesus teaching (sometime, due to exterior pressure this is impossible), but as long as one has strived to it, and is repentent about one's sins. That where it really lies for me, striving, is not the same as actually living like that. So, if you mess up due to you're choice of actions but you truly sorry, then you may not have lived as jesus said in that moment, but are now that you are truly repentent. Repentence is a keyston in how to believe in jesus.
So then what of the person who hardly sins and is sorry. Does it matter if he asks Jesus to forgive him? Is asking for gods forgiveness enough. Whoever or whatever that maybe? Does it matter?
Would such a person be a Christian in your book? What if one were to ask for Jesus to forgive him without believing he was god? Maybe he is god , but thats not the same as believing. I say the best we can do is try to follow the teachings of Jesus as we perceive them. Perception is everything. In my book if you are a follower of Christs teachings you are a christian.