Open Loops

When we leave apps open in our phone it can make our phone slow. It's trying to process so much other stuff while other things are still running. 

The same thing is true for our mind. When we have tasks that are open, our brain is still thinking about them. When we finish them, our brain puts completed things into a folder and files them away. The good thing about this is when something is open you're still able to recall a lot of information about it. Once you mentally check it off, your brain starts storing it somewhere else. 

It takes discipline to work this way. In a world that is constantly trying to tug on our attention, we can often leave a lot of apps open in our brain.  That means our brain is trying to do this new task while also keeping the last one we were doing in standby. It's one of the reasons that despite how much we try and glorify it, multi-tasking is not actually more efficient. 

Here's an article summing some of this up and with some further insight on the topic.