I just can't get started ever.
I seriously need eat a big meal, shower, find the perfect comfy studying outfit, find all my notebooks and stuff, make tea before I can study. At which point I'm often hungry again so I grab a snack and check fbook/NS while I eat it and get stuck.
But once I start I can go for hours straight with only a couple 5min breaks to go to the bathroom/grab a different textbook. With an energy drink I can pretty well go 8hrs without breaks, without I generally can last 5.