How can I know which verses from the Old Testament can be applied to my life today? I used to think verses like Jeremiah 29:11 were applicable to everyone. Now I see that verse was for a specific people at a specific time and the church today often takes it out of context as if God was speaking it to us now. Since I realized this, I now question whether I’ll misinterpret other verses in the OT. I worry that I’ll believe a verse such as Proverbs 3:5-6 that says trust in the Lord with all your heart and lean not on your own understanding is for everyone only to discover later that it wasn’t.
You can tell if an Old Testament verse is meant for a specific time or people by the context in which it appears.
In the example of Jeremiah 29:11 God had Jeremiah write a letter to the Jewish exiles in Babylon (Jeremiah 29:1). He encouraged them to build houses, plant gardens, marry and have children, etc (Jeremiah 29:4-6). Then in Jeremiah 29:10 He said after 70 years He would come to them and bring them back to the promised land, because He had great plans for their future there (Jeremiah 29:11). This tells us He was speaking to the Jewish captives at the outset of the Babylonian captivity. From this we can see that Jeremiah 29:11 was intended specifically for them.
Your other example, Proverbs 3:5-6, does not contain contextual clues like those in Jeremiah 29:11. That means it’s intended for everyone.
So the general principle is to read several verses surrounding the one you’re wondering about, looking for clues that will tell you whether it was meant for a specific people or time. If you don’t find any, you can assume it’s for everyone all the time.