I believe it was Stanley Yates that I heard say something like, "One of the quickest ways to improve your playing is to play far easier music at a professional level." Regardless of exactly who said what, it is a great piece of advice.
I'll take it even further. It is always the most basic fundamentals I return to to improve my OWN playing. Coupled with that is the fact that life gets in the way. I've always considered myself a teacher and not a performer. As I've gotten older, I've chosen to not work so hard and enjoy my life outside of the practice chair. There have been times, save for an occasional demonstration in a lesson, that I've set the guitar aside for weeks at a time. Let's just say that I've become somewhat of an expert to coming back to the guitar with spaghetti hands and needing to quickly rebuild my chops...lol
Repeatedly, I've had the same experiences over and over. I return to the very beginning. Refining a single finger stroke on an open string, the most basic right hand arpeggios, introductory repertoire, slow easy scales, etc. Diving deep into that with no concern for moving forward is EXACTLY how I quickly move forward.
Dr. Todd Tipton, Noda Guitar Studio
Charlotte, NC, USA (available via Skype)