Joshua in the Old Testament was the guy who led God's people into the Promised Land after the death of Moses. Once he was "instated" the Lord spoke to him--literally spoke to him--and commissioned him for the tasks ahead--tasks that had the potential of challenging his faith. "Be strong and of good courage...Be strong and very courageous...Be strong and of good courage." Three times in a short paragraph God repeated these words, followed by three reasons why.
First, he could be strong and courageous because God was following through with His promise. (Joshua 1:6) Here's the thing. If God says it, then it will happen. Period. He is faithful to His Word. This is a place of great rest when the uncertainties of life arise. Believe.
Second, he could be strong and courageous because God's written word is true and dependable. (Joshua 1:7-8) He challenged Joshua to stay in His word, "meditate in it day and night." In essence He said, fill your heart, mind, and soul with my word because it is bread to your body. When feelings fail, His word stands as truth. Believe.
Third, he could be strong and courageous because the God of the universe was with him wherever he went. (Joshua 1:9) This is peace. To know, as children of God, that our feet will never tread on ground where God is not present and our lives will never be faced with trials that are out of His view. He is with us wherever we go; and not only that, He is able to work and move. Believe.
Uncertainties from a human perspective will come...sometimes daily. But there is a God who is never taken off-guard. And this very God wants to be in relationship with you and me. He has something to say to us this day. His instruction is for our good and His glory. Believe, even amidst seeming uncertainty.