"Beliefs" are usually learned world-views.
The socialization and development process of children is such that they usually enter adulthood with a particular set of "core beliefs" passed on from their immediate family and close friends.
Whether a particular world-view is accurate or useful is not a debate here, but it IS very important for an adult to understand the basis and practice of their beliefs from a personal, internalized perspective. A belief can only be modified if the believer has a reason to change. NOT asking questions is the surest way to remain ignorant and manipulated.
Discovering for ones self whether the tenets and practices of their "belief" (or others) are valid is an essential part of becoming an adult. The process will either strengthen a conviction that the community instruction was correct, or lead to a modification or even abandonment of the childhood belief system. "Abandonment" does not usually occur without some other, more convincing belief system available to take its place.
It is important to evaluate the basis of any world-view, and to be sure that change or modification are based on the validity of that view rather than on the preference for one social setting over another. "Changing beliefs" simply because one wants to rebel against the indoctrinator by blindly believing a different indoctrinator is just substituting one childhood for another one. It is not the development of an adult.