Healthy adult mode is a term used in schema therapy, which is a type of therapy that helps you identify and change negative patterns of thinking and behavior. Healthy adult mode represents your healthy, functional self that can cope with challenges and meet your needs.
There is no definitive answer to how long it takes to develop healthy adult mode, as it may depend on various factors such as your personality, history, goals, and motivation. However, some sources suggest that it takes about four weeks to build a new habit, which could be one way to measure your progress.
Schema therapy also involves various techniques to help you strengthen your healthy adult mode, such as imagery, imagery rescripting, role-playing, chair dialogues, homework such as journaling, flash cards, behavioral experiments etc.
You can learn more about these techniques from a qualified therapist or online resources.