In Romans 10, Paul writes about the Israelites who were truly zealous for God (which is good!) but left Jesus out (which is bad!) and therefore had to try and establish a righteousness on their own (which is impossible!) and this led to Pharasaicalism (is that even a word?).
And we can laugh at those silly Israelites, but I think the easiest thing to do for every Christian is to leave Christ out of their Christianity. There are all kinds of forces, both internal and external, that will push us away from Jesus and lead us to take our eyes off Him and put our focus on us. And if we do we’ll either end up walking away from God, or trying to establish a righteousness on our own as we walk the path of religion.
So how do we avoid that? I don’t know. Read the Gospels repeatedly? Preach the gospel to ourselves everyday? What do you think? What do you do?