Set your mind on things above, not earthly things. Colossians 3:2
Keeping your mind focused on good things is truly a discipline. When you dwell on past problems, worries, things that may happen, world issues, and a host of other things , it is nearly impossible to have peace. That is not the kind of life God wants us to live. He wants you to cast or throw your burdens on Him then walk away and trust Him to handle things. Also sitting around speculating about things can you make you almost mentally sick. Let it go and move on.
Whatever is on your mind today why not make sure it is a good and happy thought. If you start thinking about stuff you know you should not, don't even go there. If you have to, say out loud "Devil get thee behind me as I am not thinking wrong thoughts". Sounds a bit crazy if you have never done it but it sure helps, I know I have done it.
When you make it a consistent habit to 'think on things above' then you will end up in the long run being a more kind, joyful, and gentle person. Find a way to think of others more than yourself and you will start thinking right.
PRAYER: Lord I choose this day to keep my mind focused on 'things above' and get in the habit of praising you instead of having a wandering mind. In Jesus' name. Amen.