I think God has carefully designed us such that every thought we have has an emotional/spiritual effect. When such a thought is TRUE according to God, it brings us peace, joy and other “Fruits” of the Spirit. If the thoughts we have are untrue, they will bring us emotional pain and suffering. The path to personal peace is (1) learn the Truth and (2) practice believing it.
Do you see how this is similar to physical pain? Do you see how God designed physical pain the same? When we do something “wrong” for the body, we have physical pain. When we do something healthy for body, there is physical thriving and no pain. Just like our thoughts. Get it?