Bhagavad Gita, Chapter 3, Verse 27

The Gunas of Prakriti perform all action. But the man whose understanding is deluded by ego thinks, 'I am the doer.'

A lot of what feels like 'me doing this' is nature running its own machinery, and mistaking the two is where confusion starts.

The body and mind run largely on their own momentum, driven by forces well outside conscious control. The soul isn't the one performing most of it, it just quietly claims ownership out of habit, and that mistaken claim is where a lot of unnecessary weight comes from.