Worry is expensive because it is genuinely work.
The mind builds contingencies. It maps three versions of Thursday and works out what would be said in each of them, while you are standing in a queue for coffee looking, to anyone watching, like a person doing nothing at all. That is labour. It is why you can spend an entire day sitting down and stand up shattered.
And it is doing it on your behalf. Underneath all that rehearsing is an attempt to keep you safe by making sure nothing ever turns up unprepared for.
You can be grateful for the overtime and still notice how much of the week it is quietly billing you for.