The week is the right unit of time to plan. It's long enough that you can plan holistically and not just deal with crises of each individual day. The parameters are well known: You know what's going on in your life. So you can plan the next week or so with reasonable certainty.
In the final installment of the master class based on her book “Tranquility by Tuesday,” productivity expert Laura Vanderkam says nailing your work-life balance comes down to how you use your Fridays.