I feel that understanding why you act in certain ways is more effective than repeating affirmations to yourself. An affirmation is something like “Every day in every way I am getting better and better.”
Affirmations seem to affect the very top levels of your decision processes, not the emotional centers. Unless you generate the emotion it loses the effectiveness. I think real change has to come by living in harmony with your principles and values. These are your core drivers of action, everything flows from them.
Principles are what you consider right-and-wrong. They are how you think you should act. Values are what you believe is important in the long-term. They are what pull you.
What are yours? Are you following them now?
Spend your effort understanding your principles and values. Apply your morals throughout life and build what you value. That’s more effective than repeating affirmations you may not deeply believe.