I guess I really don't know the difference between spiritual discipline and just something bad happening in life. Maybe there isn't a difference, but if there is, I don't tend to recognize it - at least not when it's happening. When bad things happen, like anyone, I tend to complain and not really find anything good in it. I'm not a big wallower in things - but at the same time I don't really appreciate what appears to be negativity happening in my life.
That having been said, there are alot of bad things that have happened that I can look back on and realize that if they didn't happen, my worldview would be very different. For example I wouldn't understand the nastiness of stereotyping if I hadn't experienced it myself and seen and felt it's effects... I wouldn't understand sexism unless I had experienced it myself. What these experiences have given me is a deep empathy for those who experience such things on a regular basis. I guess you can say I can learn from experiences. I think that's really the key to what the author of Hebrews is suggesting - that we do have experiences - some good, some bad. Some of the bad ones, and maybe even some of the good ones, are really spiritual discipline - God showing us something that we need to learn. I'm not sure that makes it any easier to take when it's happening, and usually we have to really wait for some time to pass before we can look back on anything and see how something good really did come out of it.