Primacy, the state of being first, often creates a strong impression which may be very difficult to change. Things learned first create a strong impression in the mind that is difficult to erase. 'Unteaching' or erasing from the mind incorrect first impressions is harder than teaching them correctly in the first place. If, for example, a mother is taught a faulty technique about preparation of replacement feeding (formula, instead of breastfeeding), you as a health educator will have a difficult task correcting bad habits and 'reteaching' correct ones.
The learner's first experience should be positive, functional and lay the foundation for all that is to follow. As a health educator you should present your subject matter in a logical order, step by step, making sure the audience has already learned and understood the preceding step.