Isn't the Christian faith just a constant battle to try and overcome the natural instincts that their God...?

Actually, it's the same for everyone, Christian or not. Yes, we Christians try to overcome our nature and wants in order to serve God since our natural instincts and wants are wrong, but all men strive to overcome their nature. I know you're trying to exclude the base right and wrong, but by including religion, you've thrown right and wrong into the mix. All men and women try to overcome their instincts and emotions in life, that's what trying to live a moral life is: overcoming our natural instincts and emotions. When we're angry or upset, we try to overcome those emotions and not give in to our instincts which would be to lash out or hurt others. Or if we see a girl or guy that attracts us. Our base base emotions is arousal and our natural instinct would compel us to just have sex with her or him just for the sake of satisfying our instincts without regard for the other person, and that's wrong. Our natural instincts are self-preservation and only being concerned with our own desires, which in order to live a moral and good life(Christian or not), we have to over come our natural instincts or else our world would be cruelty and chaos.