When you're working in an office and your mind starts to wonder, it's super easy to just hang out at your desk and look like you're working. Not a big deal. 

However, with remote work, nobody is there to give you credit for just sitting there, staring at the screen, and doing nothing. You only get credit when you actually get work done. 

That means that when my mind starts to wonder and I can no longer concentrate, it's a lot more productive for me to step away, take a walk, eat something, take a nap, etc than to just keep sitting there doing nothing. 

This is a good thing - as humans, it is natural for us to get tired and break our focus. It's our body's way of telling us we need a break. But in an office, you're judged for taking a break, so you keep being unproductive, simply looking productive at some points in the day. 

With remote work, when your body tells you to take a break, you need to take a break so you can actually be productive afterwards.