Can you imagine that you might have once gone to the hospital, seen a doctor, given a prescription, came back home and started your dose, days later, you start feeling well, but only to be told later that the medication you were given was not actual medication. Maybe it was a sugar pill, or even a saline solution.
That's what we call the placebo effect, ohh, and you might also want to know about its evil twin, the nocebo effect.