The programing of our subconscious is in constant evolution

The subconscious mind is the guardian of memories stored as beliefs, emotions, and images. These constitute a programing that impacts our current perceptions, triggers our emotions, and influences our behavior.

This programing is constantly in evolution due to the new information we gather every day. Before the age of seven to nine, the new information goes almost directly to the subconscious programing as soon as the information has enough emotions, trust, or repetition attached to it. After, when we are older, the conscious mind acts as a filter that keeps the unconscious programing mostly stable in spite of the new information.
It is possible to go over the filter of the conscious mind, but it requires specific circumstances such as repetition — it is used in advertising — or hypnosis.

The language of the subconscious follows many rules.

When the required circumstances are present, modification of the programing becomes possible and is effective as soon as it is done in the language of the subconscious.

The syntax of the suggestions must follow many rules to reach their goals.

The subconscious needs short and simple sentences. It understands every thing on a primary level. For example, if you say “you can do it” to get some motivation for doing something, the subconscious programs that you are able to do it, it does not program that you are going to do it.
Also, the subconscious does not understand the negation in a sentence. So it is important to use active verbs. If you say “don’t lie”, the subconscious think about lying. Instead you must say “tell the truth”. If you are not careful you can end up with the exact opposite effect. It is something you can keep in mind when you talk to children.
Moreover, the subconscious understands no other tenses than the present tense.
Finally, the message is more effective if it elicits strong images.

When they are written correctly, suggestions repeated in hypnosis are powerful tools to reach your goals. If they do not respect the rules of the language of the unconscious, they can be ineffective or worse, leading to the opposite result.