Each day is a precious gift from God. But so often we get stuck being upset about yesterday or worrying about tomorrow. God is asking us to try to live in the gift of the present moment and trust Him.
How do we do that? Just start by noticing when you are ruminating on something from the past or worrying about something in the future. Bring your thoughts back to the present moment. Then notice God and give Him thanks. Say a prayer. Ask for help.
I can talk to you more about this if you'd like.