The Bible has a lot to say about living in a spirit of thanksgiving rather than one of worry.
It's simple to understand, but so often thanksgiving takes a back seat to worry.
So often the cares for tomorrow bring a spirit of anxiety rather than a spirit of thankfulness to God right now for all He has done and is continuing to do.
Paul's epistles convict me of this so much. He writes in Philippians 1:12-13, while imprisoned:
"I want you to know, brothers, that what has happened to me has really served to advance the gospel, so that it has become known throughout the whole imperial guard and to all the rest that my imprisonment is for Christ."
Paul had a lot he could've worried about; A lot of unknowns that he could have been anxious about. Instead, he found reason to give thanks in his current circumstance. He replaced His worries with the greater purpose of advancing the Gospel, and I'm sure his attitude of thanksgiving testified greatly within the prison.
If you can't find anything else, live with thanksgiving in your heart because of what Christ did on the cross. But I think if we look close enough, there are hundreds upon hundreds of things to give thanks over, rather than worry.
You can't change tomorrow. You can give thanks today.