In this chapter, one of the things Paul writes about is how the Gentiles were given the opportunity to come to into a relationship with God. He compares it to the grafting process a gardener uses. A branch is removed from a healthy tree to create a spot to attach a branch from another tree. The branch removed is likened to the Jews, and the one grafted on to the Gentiles.
If one takes the analogy too far, one could think the Jews were removed in order to make room for the Gentiles, that God had once chosen the Jews, but was now choosing the Gentiles. Paul argues this is not the case. The Jews were cut off because of their unbelief. They had taken their relationship with God for granted and drifted fear away from Him.
This should be a warning to us. What are we doing to strengthen our relationship with God? To avoid taking God for granted? If you look at your daily schedule, which moments are intentionally planned to nurture your faith?
Romans 11:19-21 NLT
“Well,” you may say, “those branches were broken off to make room for me.”  Yes, but remember-those branches were broken off because they didn’t believe in Christ, and you are there because you do believe. So don’t think highly of yourself, but fear what could happen.  For if God did not spare the original branches, he won’t spare you either.