We all know that what made us happy as children may no longer apply. But is it just a matter of our tastes changing?Social psychologist Jennifer Aaker, PhD, theorizes that your happiness is not based on your likes and dislikes, but rather, the motivating forces that drive you. Our definition of happiness tends to shift every 5 or 10 years, evolving through 5 basic "chapters" throughout our lives.The first chapter lasts through your childhood and teen years, where happiness is found through discovery and excitement. You gain happiness by understanding the world around you.Most people go through the second and third chapters through their 20s and 30s, where pursuit and balance become the primary motivators in their lives. For example, success in your career may help fill your bucket in your 20s,...