Echoing Eleanor Roosevelt’s famous admonition — “When you adopt the standards and the values of someone else … you surrender your own integrity,” the longest-serving First Lady wrote in contemplating conformity and the secret of happiness, “[and] become, to the extent of your surrender, less of a human being.” — Luna adds:

When we choose Should, we’re choosing to live our life for someone or something other than ourselves. The journey to Should can be smooth, the rewards can seem clear, and the options are often plentiful.

She offers a counterpoint:

Must is different. Must is who we are, what we believe, and what we do when we are alone with our truest, most authentic self. It’s that which calls to us most deeply. It’s our convictions, our passions, our deepest held urges and desires — unavoidable, undeniable, and inexplicable. Unlike Should, Must doesn’t accept compromises.

Must is when we stop conforming to other people’s ideals and start connecting to our own — and this allows us to cultivate our full potential as individuals. To choose Must is to say yes to hard work and constant effort, to say yes to a journey without a road map or guarantees, and in so doing, to say yes to what Joseph Campbell called “the experience of being alive, so that our life experiences on the purely physical plane will have resonance within our innermost being and reality, so that we actually feel the rapture of being alive.”

Choosing Must is the greatest thing we can do with our lives.

Is Must really a choice? I mean, it's a Must, right?

I guess this is the theme of every Disney movie: Be who you are.

Not just every Disney movie. Every coming of age story.

"Must is who we are"

I imagine fear keeps us from must.

is it really so singular? each person has a must? really? 

Yes, especially since must is defined as "who we are".

Each person has a "who I am".