My teacher's teacher...

http://www.rzc.org/about/who-we-are/roshi-philip-kapleau/

He, Philip Kapleau, wrote the Three Pillars of Zen.
My teacher talks about how demanding the practice was. Austere and painful at times. And worth it. He, my teach that is, has written a book about his experiences with the Spiritual Process - hasn't published it yet. I've read most of it. It's a long book. But then any journey like this is a long one. It's decades of sitting, practicing, and deep self-discovery. Waiting for a kensho, waiting for something that signifies that your practice is becoming deeper.
It's hard to tell in any practice. It's not anything you can see. It's certainly not in how well you sit. Because it doesn't matter how long you sit for - years, decades, the pain returns - because you're body changes, that's why. Day to day, week to week, month to month and in the years. Even - it shifts from morning to night - anyone with a cold can tell you that.
It's a good book, Three Pillars of Zen - if you haven't read it. Any of Roshi Kapleau's books are a good read.
Just wanted to share that with you...