Lean on, trust in, and be confident in the Lord with all your heart and mind and do not rely on your own insight or understanding. In all your ways know, recognize, and acknowledge Him, and He will direct and make straight and plain your paths. —Proverbs 3:5-6
What do you let your mind do when you have problems? Do you try to figure things out instead of leaving them in God's capable hands?
There is the mind of the flesh, which is wrong thinking based on your thoughts and reasoning. And there is the mind of the Spirit, which is right thinking based on the Word of God and the inner promptings of the Holy Spirit. Confusion, frustration, and anxiety are the products of operating in the mind of the flesh. Joy is the product of the Spirit and of following the leading of the Spirit in prayer and fellowship with God.
If you operate in the mind of the Spirit, you can have "the peace of God, which passeth all understanding," and you can have "joy unspeakable" and be "full of glory" right in the middle of terrible trials and tribulations. (See Philippians 4:7; 1 Peter 1:8 KJV).The peace "which passeth all understanding" and "joy unspeakable" are types of peace and joy that don't make any sense. In other words, when you have these types of peace and joy within, you are happy without having any particular reason to be happy. You are happy just because you know that God is and that He is able to "direct and make straight and plain your paths" in an exceedingly, abundantly above all-you-can-ask-or-think way. You don't have to try to change yourself or anyone else—and that makes you happy.
You don't have to worry about tomorrow—and that makes you happy. You don't have to worry about yesterday—and that makes you happy. You don't have to know how to do everything—and that makes you happy. All you need to do is know the One who knows. Trying to figure things out will only wear you out. But if you trust God for the answers, you can enter His rest.
