Old habits never die, they get suppressed. The habits that are the hardest to suppress are the ones that were learned first in a situation:
The first response learned in a situation is especially persistent.
Please note that the Primacy Principle applies to the first response, which can occur at any age. In the normal course of events, people encounter situations for the first time during childhood. This means that many of our persistent habits were acquired when we were children. Indeed, we may have long since forgotten the specific episodes, and we only know that we like some things and don't like others. But as long as you are being exposed to new situations, be it a new field of study or a different style of cooking, your first reactions shape your future attitudes.
The Primacy Principle is indifferent in regard to the desirability of the response. A person who had happy first experiences in learning how to swim can endure many later discomforts and still love to swim. However, if those first experiences were fearful, the person is likely to avoid water even after some pleasant times. The person who "hates math," "loves rock-and-roll," "can't stand fish," "can't get enough T.V." etc., illustrates primacy in action.
There are two morals to the Primacy Principle. First, you'll have to be constantly alert to keep old bad habits in check. Second, always try to learn the right way first. Start very new venture with a positive attitude and a commitment to make it work.