Due to varied outcomes depending on outlook, it is sometimes called the 'expectancy effect,' and doesn't have to be a chemical treatment. Listening to a tone that has been 'experimentally shown to influence/diminish/ improve performance' will show an effect. This is why personal anecdotes can't be relied upon. If I pay for a quack treatment that had done wonders to treat my complaints, you may feel and believe it works due to nothing more than expectation. The take away is that you should choose to believe your efforts & choices are mightily helpful when committing to them!