You're procrastinating because you have some anxiety based on overestimation of the effort that the task will require and underestimation fo the pain that it will be to rush it at last minute. To prevent your brain from going wild, split into little easy tasks, start with something that seems pleasant or easy to do in 5 min and you may manage to focus for longer, or take a break and set another 5 min task. You can also add some reward, like I'll eat this chocolate cookie or watch this cool video after I have completed this much.