Positive affirmations are positive statements that you repeat to yourself in the hopes that they will transfer from your conscious mind to your subconscious mind. They can be related to self-esteem, changing a habit or eliminating negative self talk. Examples of affirmations are things like "I am understanding of other points of view" or "I will not compare myself to strangers in the internet". The process involves repeating these statements to yourself either out loud or in you mind until they soak in to your subconscious mind. Repeating the statements becomes a part of the daily routine of daily life and as they become something that you hear all the time, they begin to change your thinking patterns and eliminate negative thinking.
This process of self affirmation can be made as simple as reading the statements off a sticky note on your mirror as you brush your teeth, or made part of a dedicated period of repeating daily affirmations while doing nothing else.
In general, it is suggested that positive affirmations tend to be more successful, especially for beginners or in the areas of self-esteem and self affirmation, so most experts recommend you create them as positive statements rather than negative ones.
Many have pointed out similarities between the power of affirmations, so called "positive thinking" and even the "law of attraction", so whatever your choose to call them, maybe a few positive affirmations are just the thing your subconscious mind has been waiting for to break a habit or start a new one.