The two must be combined in order to know the true good news of Jesus' saving death and resurrection, and all that is implied by it. He explains this at great length in two of his letters, that to the Romans, and that to the Galatians. Instead of talking about God, people talk about 'religion'. These days, it's said that we live in a post-Christian era, that God is no longer needed or wanted. Yet the unhappiness of millions affirms that God is very much needed, and very much wanted.
Sensible rules are a part of our lives.
We can't just drive on whichever side of the road we want to - we'll kill ourselves and possibly others. It's only too clear that we don't suffer from too many rules, but rather from people choosing to disregard them. God's rules work on the same principle, and all good human laws and rules are based on them. The hurt and heartbreak caused by adultery in a marriage could be avoided if God's rules were taken as a guide, rather than personal whims and weakness. This is the greatest and the first commandment.