After initial high performance, that person lags back. Success means leaving others behind, and the guilt and fear of moving forward makes this procrastinator reduce effort. Rebelling against authority is another basis for procrastination. Revenge also comes into play. If you are angry about being assigned a certain task, put it off as long as possible.
Most procrastinators get routine work completed without much trouble.
They have to. It's the project, the creative job, or the unusual or big job that gets postponed. Psychologists recommend determining how much time is available after routine work is done. That's the amount of time available for projects. Learning to devote a half hour without stopping is considered good.