Q. If living a life as Keats is ultimately about experiencing one's true essence, what does this really mean? Can you please describe a life of expressing one's true essence.
A. Gandhi described happiness as, "when what you think, what you say, and what you do are in harmony." And if you add "and how you genuinely feel" to that maxim, you'd be very close to experiencing the answer to your question.
To express one's true essence is to be aligned from the inside out and to live consciously from that center of being, rather than being unconsciously pushed and pulled by one's environment and mental conditioning.
Expressing one's true essence means being 100% comfortable in every and all situations. It means never looking up or looking down on anyone or anything. And it means interacting with others (and with every thing) in a caring and considerate way, being respectful of their essence, which is exactly the same underlying, egoless essence as yours.