A post hypnotic suggestion refers to a suggestion given to you whilst in the hypnotic state that leads to a certain behavioural response after you emerge from trance.
An example might be something like, “Each time you take a nice, slow, deep breath, you will feel a sense of inner calm flowing through you.”
Or perhaps something like, “After you emerge from hypnosis the colour red will appear brighter than usual. And when you see the colour red it will remind you of your resources, helping you to… feel calmer and more in control.” (The bold text here highlights an embedded command, often delivered after a slight pause and with a lowered tone of voice).
Remember, in the REM state you are more suggestible. Thus, these post hypnotic suggestions (and embedded commands) are an important part of hypnotherapy. They are accepted more easily by the subconscious mind and later acted upon, often automatically, without the need for conscious intention.
What this means is that you might spontaneously take a deep breath in a certain situation (without knowing why or even noticing that you did so) and consequently feel a sense of inner calm. The subconscious mind triggered the deep breath.
Same with the colour red; you might not pay any more attention than usual to the colour red (on a conscious level) but the subconscious responds by helping you remember your resources and consequently feel calmer and more in control, wherever you happen to be.
