Here's a cool short video on the potential problems with checking your phone before bed. It can mess up your sleep - and sleep is supremely important for your mental performance and for your health.
Personally I cheat a bit. I regularly read books on my smartphone as I'm getting ready for sleep. But I use the Kindle app with black background and white text. Plus I minimize the brightness of the screen and text. I can still comfortably read in a pitch dark room, but there's a minimal amount of light and I tend to get sleepy and fall asleep pretty fast.
What's your phone habits before bed?