Often, we worry about things that haven't happened yet or may never happen. Worry steals away our joy and makes us incapable of completing the tasks God wants us to accomplish throughout our lives. When we are stuck in worry, our minds are occupied, making it difficult to pray and listen to God. 
Apart from God, nothing in this world is guaranteed, including our tomorrow. Of course, we all wish to see tomorrow, but there's no guarantee that tomorrow will come - only God knows for sure. Therefore, we are commanded not to worry, fear, or be anxious about tomorrow and what it may bring.
If you begin to get anxious about what may or may not happen, spend time with God in prayer. Put your focus on Jesus instead of the 'what ifs.' When you put your worries in God's hands, you will find peace.

Dear Heavenly Father, help me not worry about tomorrow but focus on You. I am so thankful for everything You've done for me, and I pray that You will continue blessing me in all areas of my life. Help me remember that Your plans are to prosper me and not to harm me, regardless of the challenges that I face today. Father, I give all my worries to You. Let Your peace replace my worries.
In Jesus's name I pray. Amen.