What the quote means is that it is easy to fall into darkness if you are not careful. I can't remember the entire context....being a Christian doesn't mean that you are infallible.
And, nothing anyone else has posted goes against what I said...I just don't think I was clear because what happened to me was so horrible an experience...
Yoga is a spiritual practice....Pilates, which has poses very similar to the yogic asanas is NOT a spiritual practice. They are the same, yet different.
Plus, I didn't say that it was ABSOLUTELY not possible to separate the spiritual from the physical...I merely stated that I wasn't too sure if it really was.