A great short video on the science of procrastination and the role of hyperbolic discounting.
Basically, when we procrastinate, we often choose things like video games, facebook, twitter, and even email. These options are very attractive because they provide small quick dopamine rewards, unlike what we're avoiding, which is likely a one time future reward.
Human motivation is highly influenced by how imminent the reward is perceived to be — meaning, the further away the reward is, the more you discount its value. This is often referred to as Present bias, or Hyperbolic discounting.