Nothing is a greater robber of joy than WORRY. From a spiritual standpoint, worry is wrong thinking (the mind) and wrong feelings (the heart) about circumstances, people, and things.
The antidote to worry is the secure mind: “And the peace of God…shall keep [garrison, guard like soldier] your hearts and minds through Christ Jesus!”
When you have the secure mind, the peace of God guards (v. 7) you and the God of peace guides you (v. 9).