Well you have ~30% chance that anything will work for you if administered correctly (with appropriate procedures, this is the key), even pure sugar or so called healer. Placebo, it works even when you know its just a sugar pill, but less effectively, around ~15% chance. It can really work, if not today then maybe tomorrow, it doesn't really matter, because chances are more or less constant, so you can try again whenever. Strange, but true, there are some papers on this phenomenon, but I'm too lazy to search for them right now.