When working on self-development, you have to start with something. In philosophy, Descartes doubted everything he could until he reached his core realization: "I think, therefore I am." In self-development, the core is not thought but values. What are your core values? That question becomes the basis of your journey of improvement.
Each of us has a unique set of values. They may be similar to others, but never an exact copy. It is one of the qualities which make us unique. You can spend a lifetime knowing another person, but unless you recognize the differences in core values that person will still surprise you.
Our values come from a variety of sources. Some of the more common sources are upbringing, organizations, and readings. Our parents start the process by teaching us as children; we watch and listen to our parents, learning what they value, acting in ways we hope they would approve. To this is added the organizations we are part of: the schools, the churches, the clubs, the troops. These organizations can be formal or informal, but all organizations are based on some set of principles which we learn and abide by, at least as long as we are a member of the group. The books we read provide another source of value input; books we have to read (such as for school) and books we choose to read. Other sources include people we meet, our culture, the media, and more.
All of these sources combine to create our own unique set of core values. These values can change over time, either consciously or subconsciously. Until we learn our core principles, including the ones buried deep within, we cannot truly know ourselves. Recognize that core values are neither all good nor all bad, but they are one of the foundations of our actions.
Our beliefs determine what we like and don't like, and how strong our likings are. They influence our choice of friends, careers, and hobbies. They guide our choices of activities. Core values determine our goals and dreams, making some things desirable and others not. The worthiness of actions is judged by a standard set by our core values.
So, if we want to change, we need to identify our core values. This fact has been recognized by many people under many names, from Vic Johnson's "limiting beliefs" to T. Harv Eker's "mental blueprint" to Bob Proctor's "paradigms." Regardless of what they are called, change will only come from recognition of your unique set of core values and a conscious decision to change those values which are holding you back.
The phrase "Know thyself" has been around for a long time. Learning your personal set of core values is a key step in knowing yourself. Only after you know yourself can you begin to develop yourself. This is true self awareness.