Jeremiah is a kinda depressing book overall. Jeremiah was basically the last prophet to warn Jerusalem of its impending doom, but the Jews were so set on their idols, they ignored him until finally, boom. Babylon shows up in chapter 39. Surprise, surprise. When you ignore God, it never goes well.
That being said, Jeremiah was still affected by their poor choices, cuz all of Jerusalem was. Still, the Lord promised him that, because he was faithful (unlike everyone else), he would be preserved. God watches out for his faithful children; this is a fact. Even when all hell breaks loose, and when society itself has crumbled around you, God will protect you. It’s good to be reminded of that in this day and age, am I right?