Revision is only effective when you're actually doing it. It is so easy to think we've spent hours working, only to realise we actually spent most of it scrolling through the various social media accounts... checking messages... or worse still... searching exam gifs to post to friends...! :D
In order to optimise your revision time, you need to cut out distractions. One big distraction is mobile phones. Try putting your mobile in a different room, or hiding it out of sight. When you're on a revision break, try doing something different than checking your phone. Try having a dance to your favourite music, going for a walk or doing a quick fitness video.
Time flies when you're having fun, so make sure your breaks don't last longer than planned. Give yourself a set time to work and when you're on a break make sure you set an alarm so you can get back on track.