When you design a product that you want users to become habituated to, you should consider the Hook model, says design researcher Nir Eyal. That includes determining a trigger, action and reward -- as well as what the user will invest into it. "Your phones, tables and chairs, these things depreciate. They lose value with time. But habit-forming technology has the opportunity to appreciate," Eyal said. "It should get better the more you use it."