You don’t! Every Bars session is different and there is no way to predict exactly what will “happen.” The guideline that best applies is that the worst you will feel is like you had a great massage, and the best that can happen is your whole life can change.
In some Bars sessions you may sleep during the whole session with waking up feeling fully refreshed, energised and alive. In other sessions, you’ll be wide awake and talking. Every session is different.