I was reading Jeremiah 14, when The Lord rejects His people because of their ‘wandering’ and their repentance is to no avail. It’s a stark warning
Yes but that was speaking of the Jews in their constant disobedience and following God's instruction. They were a rebellious children but he still loved them and called them his people. Salvation on the other hand was done when Jesus proclaimed the words it is finnished and gave the final breath of his life to God.
Your salvation is set in stone the moment he comes into your heart, there is nothing that be taken from his hands once it is his and your sins and doubts and fear can never break the covanent he made. In fact the reality you are worried about this is only proof of your salvation. Do you know how many who call themselves Christians don't even bother to consider their sins or how they dishonor God in their reckless abandon to do as they please?
We don't try to not sin for salvation we try to be pure and holy but also to honor his work on the cross. Grace is abundant but is not to be taken for granted or advantage of.
Don't fret about your failings and sin or your salvation rest in his peace and grace and draw closer to him this is how the spirit works as we draw closer to his heart he flows more and more this is not simply a thing we ought to as believers it is the key to his heart.