YouTube watch history makes it easy to find videos you recently watched, and, when it’s turned on, allows YouTube to give relevant video recommendations. You can control your watch history by deleting or turning off your history. If you delete some or all of your watch history, YouTube won’t base future video recommendations on that content. Any videos that you watch while history is turned off won't show up in your history. 

Assuming viewing history is enabled, you'll then be shown everything you've watched recently on YouTube, with the most recent views at the top. There may well be a few videos you've forgotten about here; this is the place to go to if you want to watch again something good or useful that you've seen lately. 

If you really want to clean up your YouTube page, you do need to delete that history because otherwise, you’ll still be getting recommendations based on everything you watched before you hit that Pause button.