Malachi 4:
1. "For behold, the day is coming, burning like an oven, and all the proud, yes, all who do wickedly will be stubble. And the day which is coming shall burn them up,'' says the Lord of hosts, "that will leave them neither root nor branch.
2. But to you who fear My name the Sun of Righteousness shall arise with healing in His wings; and you shall go out and grow fat like stall-fed calves.
NKJV

When God tells us that "the day" is coming, we automatically think it means the end of the world when He will sit as Judge, and this is true.
However, the Bible also speaks of "the day" in other ways. Consider these words of the Lord Jesus:

Matt 6 : 34. "Therefore do not worry about tomorrow, for tomorrow will worry about its own things. Sufficient for THE DAY is its own trouble."
NKJV
Matt 6 : 34. "So don't be anxious about tomorrow. God will take care of your tomorrow too. Live one day at a time."
LB

Here God is saying to us that "the day" - which is today - can often feel like a hot oven, and that can cause us to worry about how hot tomorrow might be. But His instruction about tomorrow is that we should not stretch ourselves out worrying about it in advance.

The main reason not to worry about tomorrow is that many times the bad things we worry about concerning tomorrow, never happen.

God knows that if instead of stretching ourselves out worrying about tomorrow, we choose alternatively to thank Him for being our God, and always being there for us, our thankful praise gives God the permission to take care of the things we are afraid of concerning the coming vital day: tomorrow.

Prayer:
Father, today I thank You for being my God: for always being there for me, even when life seems too hot to handle.
I choose to put my trust in You for today and I choose to thank You for taking care of me in the future,
in Jesus' name,
Amen.