For youtube specifically, I found this great snippet for ublock origin. It removes (almost) all recommendations in youtube, which makes it much easier to quit after just one video:
www.youtube.com###secondary
www.youtube.com##ytd-browse[page-subtype="home"] #primary
www.youtube.com##.ytp-show-tiles.ytp-endscreen-paginate.videowall-endscreen.ytp-player-content.html5-endscreen
Source: https://pawelurbanek.com/youtube-addiction-selfcontrol