Engagement, visceral or intellectual, elicits the desire of perseverance and concentration. Underserved stimulus needs of nurture for intelligence via optimal reciprocal engagement, include steady emotional support, exploration and fun, active participation, sensory stimulation, with opportunity for social interaction, freedom from undue pressure and distress though suffused with a degree of pleasurable intensity or: eustress, with varied selection and alternatives of successive novel challenges neither too easy and boring nor too difficult and frustrating, promoting lifelong growth in a broad range of skills and interests, intellectual, physical, aesthetic, social and emotional.

According to Freud, the reality principle in the mind, playing out likely scenarios, weighs the costs and benefits of any effort before deciding either to act upon and gratify or else to restrain and abandon an impulse arising in accordance with the pleasure principle. And this interplay of the pleasure principle checked by the reality principle is obviously fundamental to all motivation and values, being crucial because Eudemonia, authentic well being, arises from human interchange suitable to fulfill intrinsic stimulus needs in harmony with personal values. -not merely character, even howsoever sterling, in the abstract, but real opportunity for life lead in integrity. Thus, happiness comes in meeting ones needs for capable interaction with responsible others, partaking together in that very interplay of the pleasure and reality principles that imbues living with meaningful relevant value and autonomy.