You must realise by now that your conscious mind is the “watchman at the gate,” and its chief function is to protect your subconscious mind from false impressions. You are now aware of one of the basic laws of mind: Your subconscious mind is amenable to suggestion. As you know, your subconscious mind does not make comparisons, or contrasts, neither does it reason and think things out for itself. This latter function belongs to your conscious mind. It simply reacts to the impressions given to it by your conscious mind. It does not show a preference for one course of action over another.
The following is a classic example of the tremendous power of suggestion. Suppose you approach a timid-looking passenger on board ship and say to him something like this: “You look very ill. How pale you are! I feel certain you are going to be seasick. Let me help you to your cabin.” The passenger turns pale. Your suggestion of seasickness associates itself with his own fears and forebodings. He accepts your aid down to the berth, and there your negative suggestion, which was accepted by him, is realised.
Extract from the book “The Power of your Subconscious Mind” by Joseph Murphy