The short answer is self-knowledge. It means that you know yourself as you truly are. Early mental models and the illusions needed to sustain them require a lot of energy, sometimes against mountains of evidence to the contrary. We have to not see to not change.
It is like an unsophisticated buyer who unknowingly purchases an “out of tune” Ferrari operating on eight of its potential twelve cylinders. It looks like a Ferrari and still drives good but potential energy is being wasted because it is not performing anywhere close to the limits of its engineering and design. If the new owner is not curious about possibilities she/he may accept the Ferrari’s maimed performance as what is possible, and never experience the exhilaration that could be result from a simple (but not cheap) tune up.
We are sometimes like that uninformed Ferrari owner. We limit our curiosity about ourselves and choose to operate on the basis of outdated models that require energy consuming illusions to maintain them. Since a lot of this operates outside of awareness we believe that our functioning is closer to our potential than is actually the case. Self-knowledge may be thought of as the human counterpart of reengaging the Ferrari’s additional four cylinders and synchronizing them to operate along with their counterparts to achieve peak efficiency.
Harnessing our unrealized potential is what could make it possible to give without being depleted and end each day with abundant energy for living. But, you must be willing to take an honest look at how you function and ask if your limitations are not actually self-imposed.