"Therefore do not be anxious about tomorrow, for tomorrow will be anxious for itself. Let the day's own trouble be sufficient for the day." Matthew 6:34
If I let myself, I will start a day thinking about a small problem, and then another problem, and then a concern that needs tending to, a person I need to catch up with, an errand that should have been done yesterday, an emergency that will inevitably come up during the day, and by the time I got to bed at night- all I've done is worry.
What a waste of time. I have to remind myself to do more instead of worry more. Then, I will have less to worry about.