Affirmations do not work. In fact, a couple of years ago, a study was carried to see how affirmations work on people and it was discovered that affirmations make people more miserable. If you want to build self esteem, you need to improve yourself in the areas where you are less confident. If you have low esteem because you are not good at something, you need to improve your knowledge and skills build expertise. If you have low esteem because you do not have great appearance, you will have to dress properly to boost self confidence. Don't remind yourself that you are best, don't act like you are the best. By doing it you will only be lying to yourself. Instead realize your shortcomings and work hard to overcome your short coming.