It's not the three minutes it will take to do this favor for you. Everyone has three minutes.
And it's not even the noise and the wear and tear of the mental clutch as we shift from one task to another.
For me, and for many people, it's the leakage of mental bandwidth.
Fear is the enemy of creativity and innovation and of starting things. The resistance hates those things—they are risky, they might not work, so the resistance pushes us not to do them.
On the other hand, it loves the notion of to-do lists and favors and multi-tasking and yes, continual partial attention, because those are perfect hiding places, perfect places to avoid the scary work but still be able to point to a day's work, well done.
But if you have nothing else due, nothing else to do, no other measurable output but that thing you've promised yourself, if all your mental bandwidth is focused on this one and this only, then yep, you can bet that you will get more brave.
Before internet connectivity poured from the sky, I was able to get on a train, plug in my Mac and have nothing to do for four hours but write. And so I wrote. I once bought a round trip ticket to nowhere just to eliminate every possible alternative… pure, unadulterated mental bandwidth.
Plenty of places to run, plenty of places to hide. None of them are as important as shipping your best work today.