I think the purpose of falling back a few levels is to come back stronger, and if you do the same level failing it every time, you are getting stronger but at the same time you are failing exercises and the level, which has some affect on your mind, you might feel unhappy and not motivated to continue, where as when you do the lower levels, you are sure that you can do them and feel stronger for the failed level. That's what I think of it, I think 2-3 levels back is fine, I'm not sure if this is a good answer, you should wait for Chris, he might just make a video of it. Good luck! :)