The Mishna says, "Hevey mechasheiv hefseida neged scharah."
Why mechasheiv?
Because the yetzer hara doesn't want us to make a cheshbon.
It wants us to be filled with a ruach shtus and close our eyes and go with the inertia of doing an aveira.
If you think about it in advance and calculate what you will be doing, known as mindfulness, you will use your taivos for good, not bad.