Breathe

Do breathing exercises and improve eyesight instead of wasting time on the web.

Makes you wait 25 seconds before visiting distracting sites (which you define in the extension options). Allows you ten minutes on said sites, then you'll have to wait again. Helps break the habit of mindlessly looping through Reddit, Twitter, Facebook, Instagram, etc. Why not block those sites entirely? Because you'll probably disable this extension and be back at square one if you try to completely cut those sites off.