Facebook and Buzzfeed :(
I kept checking every notification which pulled me in to a black hole of surfing and I ended up using 2 or so hours on Facebook and Internet stuff a day (this was only at work so my days got so long because I had to stay longer and actually do my job). Found out I was addicted, read some articles about work productivity and how to be more effective at work, deleted social apps from my phone and only check notifications once a day, and now my days are much shorter and I actually feel relieved and free :)