Playing music is a mental game, not a physical one. I say this all the time in my private lessons, and I’ve mentioned it on this blog before also. Certain aspects of playing an instrument revolve around physical capabilities, but even then the mental component plays a prominent role. Therefore, focus is your biggest asset.
Earlier today I was teaching a lesson and the student was struggling with playing a particular groove. The struggle, however, was with playing the groove more than a couple times in a row. He could play it fine for the first measure, then straight into the second measure with no problem, but he would inevitably fall apart somewhere in the third measure. We talked about it a little and I asked him why the third measure was different. The groove doesn’t change on the third time around, and in playing the groove correctly for the first two bars he was proving that he could do it. He thought about it and realized that he was losing focus after the first couple times. He was pulling the rug out from under himself by taking away the most important ingredient.
That is pretty much always going to be the answer for why anyone will struggle with anything on the drumset. Unless you’re talking about blazing cross-chops and stick spinning tricks, the primary (and often ONLY) obstacle between you and being able to play the groove/fill you want to play is focus.
SUMMARY: If you have not yet considered focus to be the main issue in playing drums, then you will probably find every element of your playing to be easier once you put your focusing at the top of your priority list.