Your best self could be defined as being at peace with yourself and in balance/harmony with others. When do you feel best about yourself? What activities are you doing? What thoughts are you thinking? What is it that makes you feel your best about yourself?
Write those things down and reflect on them.
What do you do that makes you feel most alive and vibrant?
When do you do those things that make you feel most alive?
What would it take to do more of those things?
What are you at your best?