Self-knowledge is knowledge and understanding of internal concepts (such as one's own motivations, strengths, and weaknesses) that have been gleaned through reflection and honesty. This is a humanistic concept in that it includes assessment and understanding of human nature, both its positive and negative aspects.
This can be a difficult journey for many people because we humans have the tendency to lie to and delude ourselves. Many also tend to have an aversion to introspection due to cultural or social stigma. However, self-knowledge is one of the main goals of psychotherapy, introspective reflection, and meditation. It also encompasses the practice of mindfulness which is the effort to try to be fully aware and "own" one's own thoughts and actions.