We can use autosuggestion consciously in our favor. We usually have a habit of telling ourselves negative information, bombarding our subconscious mind with negativity we eventually end up believing.
You can use autosuggestion by presenting your mind with repetitive thoughts (negative or positive), until those thoughts become internalized.
Autosuggestion can be used deliberately to help you shift your thoughts and beliefs. However, it is also an unintentional process. Whether you realize it or not, you are using autosuggestion to make yourself believe things.
The main thoughts in a person's conscious mind, if repeated over a long period, can train the person's subconscious mind to arrange their beliefs according to those thoughts.