Habit-forming products alleviate users' pain by relieving a pronounced itch.

When designers intentionally trick users into inviting friends or blasting a message to their social networks, they may see some initial growth, but it comes at the expense of users' goodwill and trust. When people discover they've been duped, they vent their frustration and stop using the product.

Like flossing, frequent engagement with a product, especially over a short period of time, increases the likelihood of forming new routines.

For an infrequent action to become a habit, the user must perceive a high degree of utility, either from gaining pleasure or avoiding pain.

Reducing the thinking required to take the next action increases the likelihood of the desired behavior occurring unconsciously.

Users who continually find value in a product are more likely to tell their friends about it.

As fleeting commitments, diets often fail. Thinking of dietary choices as part of who you are...can give them real staying power