Today I was listening to James Clear, author of Atomic Habits on the High Performance podcast which I'll link below. It is a really good episode!
If you don't know Atomic Habits was part of the inspiration for this group. The 66 in the name derives from the average amount of time it takes to establish a habit.
One tip James gives for maintaining habits is never miss twice. It's OK if you forget a day and miss once, just don't let it become two days! Thus begins the slippery slope.
For those of you writing your diaries I would suggest incorporating this rule. If you miss a day, don't feel you have to reset to zero. Often this will kill your morale and it's hard to get started again. Instead just get right back on the wagon and make sure you don't miss the next day.