A Practice!
The mastery requirements
The 10.000 hours rule has been endlessly promoted as the way to mastery; and while this is true for the main activity in your life, it falls short for any other activity you attempt to do.
A quick math operation reveals that by investing 8 hours a day, everyday for the next three and half years will be roughly the 10.000 hours need for mastery; those numbers are professional athletes numbers. Another quick math operation reveals that by investing 45 minutes a day, 80% of the year, it will take you 45 years to reach the 10.000 hours required for mastery.
Knowing that you will never achieve mastery discouraging at first. After all why commit thousand of hours if you can't reach the peak? I say because it is liberating, you quit looking for the workout that will finally get the results you want, the one that you finally stick to, the one you understand, the one that you don't need an entire gym floor for a single day of training.
The alternative is to choose to practice. Simple by design, the practice forces you to eliminate the dozens of ways to perform the same exercise, the ever changing equipment. Pick the least amount of equipment and reduce the exercises down to the barebones, the most pure and simple form of it. Truth be said, you won't achieve mastery with the practice either.
If mastery is unattainable by working out, but neither by practicing, then what? Should you pick between a confusing dozens of exercises for a single muscle group or do Swings for about 25 minutes each day? It's your choice, you decide. I chose the practice for myself, so I can invest the real 10.000 hours in my profession.