Treating all habits the same is like using a screwdriver for every type of screw.
Simple completion (check-in)
Ideal for: binary habits. Meditate, make the bed, take vitamins.
By time (timer)
Ideal for: activities where duration matters. Study, practice an instrument, exercise.
By measure (quantity)
Ideal for: cumulative habits. Glasses of water, fruit servings, pages read.
Strategic tip for the 66 days
During Destruction, prefer simple completion. During Installation, refine with time or measure. During Automaticity, maintain.