Mental prosperity is simply clarity of thought and and focus without worry or stress. I know without worry and stress I would have much more clarity and focus. Eliminating worry and stress can be done you just have to let God have the worry and stress by focusing your thoughts toward God, especially if you feel yourself being overwhelmed by stress. If you can read the Bible or just say a small prayer to cast the cares upon the Lord you will feel relieved.
Remember what the Bible says about worry:
Matthew 6:34 (CEV)
Don’t worry about tomorrow. It will take care of itself. You have enough to worry about today.
Who of you by worrying can add a single hour to your life?
Phillipians 4:8 (NIV)
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things.
Have I not commanded you? Be strong and courageous. Do not be afraid; do not be discouraged, for the Lord your God will be with you wherever you go.”
These scriptures tell us that God is with us and that we should not worry about tomorrow. What we should think about is God. We should strive to study and learn the word and God will bless us with peace and knowledge.
13 Brothers, I do not consider that I have made it my own. But one thing I do: forgetting what lies behind and straining forward to what lies ahead,
14 I press on toward the goal for the prize of the upward call of God in Christ Jesus.
Do not conform to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God’s will is—his good, pleasing and perfect will.