Resource for fostering internal motivation and avoid "behavior modification" techniques and other forms of external motivation (Read for both links)
Core Practice #2: Fostering internal motivation and not using rewards, bribes, incentive programs or sticker charts, which foster external motivation and which adults can use to control and manipulate children’s behavior. (Examples include “behavior modification techniques, ABA or operant conditioning programs.) If you are unfamiliar with these teachings or the research behind them, you can review these articles: The Use of Rewards and Bribes and Use of Behavior Charts.