Being great in this case does not mean being famous or heroic or some rare ideal.
It means producing a great life that you love, being fully in your power.
It means supplying yourself with all that is needed and giving to others what they need and accepting them and loving them (if you do that, you'll have plenty of being loved). It is not being dependent on others or on circumstances to make you happy or rescue you in any way. There is no dependence on approval, but you give out lots of appreciation and acknowledgement, always with lots of acceptance (and approval, in a sense).
You fill your "tank" up, so that you are centered, grounded, at peace, and able to pace yourself through the day and through your life.
You prioritize everything - who you want to be, your values, what you want to do...everything - you live purposely, aimed for the priorities.
You have a clearly writtten and memorized set of values, prioritized, that you use to guide you in your decisions. As an expression of those values, you keep yourself healthy and energetic so that you can live the great majority of your day in a high state of resourcefulness and perspective.
