It's foggy... but I do remember back to studying Mahayana Buddhism in college and reading Naagaarjuna: The Philosophy of the Middle Way (David J. Kalupahana) Oh, who am I kidding? It's not foggy at all. That class was a life-defining awakening of my intellect, because I learned a very simple but very important fact: Without the mountains and the valleys, we'd never know what the plains are.
Translation/abstraction/gross use of statement out of context solely for humor: If everything was good all the time, we'd have nothing to complain about. So stop complaining.
Mr. Kalupahana, you most certainly did change my life, but I have something to say, my Nag Champa-burning, yellow-robe-wearing friend...
Though you have made a very important contribution to the field of philosophy, I am sorry: Musicians know all about plateaus already. We don't need no stinkin' mountains to recognize that we spend most of our time on a vast plateau characterized sometimes by great bucketfuls of fun but also punctuated, alternately, by two questions:
1) "Seriously? So if I want to do this for real, then I have to do this every day? Like forever?"
2) "Why is this so hard?"
Answer: No answer. Keep doing it.
So, we keep on practicing. Every now and then, we spend a month or two just maintaining. Barely making it (but making it) to the practice space. Every now and then calling a three-hour rehearsal a substitute for true, focused practice. And making no major improvements, feeling no tingling inspiration, just doing it because it's our practice to practice.
That's the plateau, right there. A plateau that, if you keep moving forward, you find is not a plateau after all. It's just one very wide, extra long landing on the winding stairway to mastery. Perhaps you can't see the next step, but that doesn't mean it's not there.
It's there. It's always there. But there's only one way to find it: keep looking.