This is from a two-year-old Men's Journal article, but it's a good reminder that it's A-OK to forego daily hour-long workouts of moderate intensity in favor of 15-minute-long balls-to-the-wall metcons three times a week:
“If your definition of fitness is keeping fat off, having a stronger heart, and being able to endure rigorous activity, like a day of skiing,” says Nick Delgado, president of Newport Beach, California–based Ultimate Medical Research, “then you want to be doing anaerobic exercise.” As opposed to aerobics, this type of exercise involves maximum-effort training, such as sprinting and lifting weights, in which the intensity of the exercise exceeds the body’s ability to supply oxygen to muscles. “Shorter, high-intensity workouts burn off glucose much faster than long runs, so you start burning fat at a much higher rate, your heart beats so hard that it becomes stronger, and you’re pushing yourself to such extremes that anything else you do feels easier.”