Sometimes, you just can't help but swamped by many disparate issues. Worse, all of it are equally interesting and important. However, you can't possibly tackle them all at the same time. If you try to wrestle it all, you'll crash.
Pretty much like having too much tabs open on your browser and then crashing it.
One of the way to 'close the tab' is to write done. At least your mind can tick it off as done, no matter how small it is. It also helps to put some distance to the issue so you can evaluate whether you can make an impact on it or not.