If I had to chose 1 day out of the week as the most important day, honestly I’d say everyday you live is, but if I had to chose 1 day only, then for most people I would chose Sunday. Why? Because Sunday is the last day of the weekend, the day before the first day of the week. Sunday is a day we should prepare our minds, in my opinion it should be a day of resting and preparing the mind for the upcoming week. How will you approach this week, what will you be eating (meal prepping should be done today). What kind of workouts will you be doing, high rep, low rep, heavy weight light weight, cardio. Sunday is a day to prepare your mind!