Below is the number one rule to become successful when initiating a physical fitness plan...in light of having a busy life.
Be it one day in the morning, one day in the evening and weekend mornings... go for a routine you can stick with no matter what the variety of time, days and types of workouts it may be.
Reason: The body is a physical machine with a memory; muscle memory and mental discipline is quickly trained when you keep a routine regarding type of exercise, time of day, and effort level. When you begin flip flopping workouts, vary training plans, skip workouts, etc., the body weakens or overworks, and the mind has lost much of the discipline needed to attain a goal of a steady progression of physical fitness.
Solution: Be truthful with yourself. Look carefully at your calendar and for two weeks schedule times and days you know you can workout. Then, if that schedule works...stay with it. If not, tweak it...and then STICK WITH IT. After 2 months, you can re-evaluate times, days, and types of workouts, since by then both muscular and mental adaptation will have been achieved.
Variables to consider when establishing a routine: Sickness, heat, family sickness, working late, etc. Yes, expect these road blocks and others ...at least once or twice a week. There again, establish a routine which keep those situations in mind.
Routine example: Mom with child growing up and cannot be alone. Wake up an hour earlier; Mom works out first, and Dad second. Go for 2-3 week mornings. Take Monday and Friday off for mental and physical rejuvenation. Then Mom and Dad can work out during the weekend...again in the morning....but a bit later since both do not have to go to work.
(I used this routine for almost 15 years while Thomas was growing up)
Remember: when the body is feeling good, the mind responds with positive thoughts. When the mind gets weak and confused, the body responds in kind. Begin a routine physical fitness plan for both mental and physical benefits... one aspect does not work without the other. Too many people aim at just the physical realm...and sadly forget that "the body is the servant of the mind".(James Allen)