…it depends on what you change them to. The only thoughts/beliefs that will bring lasting peace/joy is the Truth of God. The way God made us is this: Believe/think the spiritual Truths, and you will live in peace/joy. Believe/think untruth, you will experience depression and anxiety. Pretty simple. Lots of other posts on here discuss this from various angles. You may need to do some work if you have too much doubt to believe what God says. There are solutions.