Recently I had a conversation with a friend and Powerlifting Athlete regarding her training and prep for her next meet. Superhuman as she may be (in the top 6% of all USA Powerlifters), she told me she is struggling with motivation. While this makes us mere mortals feel better about ourselves, my response to her was quite simple, "you don't need motivation all the time, you need discipline."
I have been training my entire life. I learned barbell movements with a broomstick as a toddler. I have spent my business and recreational life in fitness and there have been weeks and even months out of my life where I lack motivation. What turns a competitor into a champion is discipline. The path to reaching your goals, no matter how big or small is discipline.
There are ALWAYS going to be days when you're "too busy", "too tired", or simply just don't feel like training or climbing on a stairmill for the 7th YEAR in a row. Reaching fitness or even life goals is not about trying to find a way to stay motivated all the time. No one is motivated all the time. Discipline is simply the act of doing something because it is required to be done to get from point A to point B. Following a proper nutrition plan is discipline, not because it tastes good. Completing daily cardio is discipline, not because anyone looks forward to the daily stairmill. Finishing a workout even when the weights are heavier than they are supposed to be that day is discipline. You don't simply give up and say, "I just don't have it today." There will always be days when you "just don't have it". The difference is whether you stay to finish your work or you pack it in and head home. Very few disciplined individuals ever don't reach their goals. Discipline is seeing it through to the end. Seeing it through past injuries, illness and personal or professional setbacks. No matter what, you still do the work. That's discipline.
The best part about discipline is that it is a learned behavior. Motivation cannot be learned. You can't just wake up one day and say "I'm going to be motivated today." But you CAN wake up and get out of the bed and onto your cardio even though you don't want to. No matter what, day in and day out, discipline does the work that motivation doesn't want to and on those glorious days where you find motivation on top of your discipline, magical things happen.
"Greatness occurs through the discipline it takes to attain it." -Adam Moore