This week's Torah portion speaks of a Divine promise: "And it shall come to pass if you listen to these laws and keep them and do them, God your Lord will keep the covenant for you […] and will love you and bless you and multiply you.".
Later the Torah speaks of the opposite side: "And it shall come to pass if you forget God your Lord […] they shall be lost."«
It's very simple. If we observe His mitzvot, are careful with our words, etc., God does His part and blesses us. If not, He doesn't.
However, it's not that simple. To paraphrase the language of our sages, what does this resemble? A king of flesh and blood, whose son received detailed instructions on how to behave and failed to follow them. He was warned through advisors and those close to the king, but he didn't improve, or he improved temporarily and then regressed. This happened again and again. How does the story end? The king always gives another chance. Why? Because it's his son.
Likewise, we are the children of God. Yes, I know, all creatures are, but we are the firstborn, the chosen ones from among all humanity. There is always another opportunity. There is always a chance to do Teshuvah and return to God.
That's what Judaism is all about. God, our Merciful Father, always has another opportunity ready, always has his hand outstretched; it's up to us to take it.