• Restricting hours: set aside a certain chunk of time for work and don’t work outside of it. For example, the Pomodoro technique for working in short bursts of time.
• Restricting workload: instead of deciding on a set number of hours, you decide on a set number of ...

• Tasks are discrete and fairly predictable.
• You might be tempted to fill up time without making real progress
• The tasks are frequently repeated, and therefore easier to estimate.

• It’s unclear the time and effort required to complete the task.
• The work itself is ambiguous and may require a lot of trial-and-error.
• The work is continuous and can’t be easily divided into discrete chunks.

The advantage of constraining tasks is that it focuses directly on the object of productivity: whatever you’re trying to accomplish: you can't fool yourself into believing you’re working hard but you’re not actually accomplishing much.

Disadvantage: tasks can often be ambiguous or...