> You'd think after years of procrastinating and as a result, getting even worse emotions, the brain would learn to not procrastinate in order to avoid unpleasant emotions.

An alternative is that the reinforcement mechanism in the brain only responds to rewards on a short timescale. The reward from procrastination (not having to face xyz) comes immediately. The punishment from procrastination (your job/life is in shambles) comes months or years later. So you end up adopting a policy of procrastination.