A Chrome extension that lets you focus on your video, and hides everything else. https://chrome.google.com/webstore/detail/focus-for-youtube/faidkelbcgjlpcigmdbhcfbonjelcbfo
It's surprising how quickly one (occasionally myself) can descend into the YouTube Spiral in a few clicks.
We've all done it. You start looking at a short clip ... and end up clicking on related content after related content for hours and hours on end. It's all just far toooooooo interesting!
This Chrome extension hides the related/recommended videos, the trending videos feed and comments. It let's you regain focus on only what you really needed to see.