Merriam-Webster describes Duende as a mystical force. They quote the poet Federico Garcia Lorca that Duende "is a power and not a behavior... a struggle and not a concept." Oof! What does that even mean?
I think when a piece of art touches your soul, that's Duende. If it is a power, then some have it and some don't. I have played with two people in my life who could summon Duende. Both had great personal magnetism in addition to their musical talent.
I've had ups and downs with music. Some efforts rewarded and others rebuffed. Some successes are a mystery, why one song and not another? It occurs to me though that striving to make music to please one's self is the path to making music that reaches others. You have to follow your heart.
But most important, when your heart cries out, and you make music, it's only personal until you play it for someone else. When others find their story in the song you made, it's not about you anymore. When you become a raindrop in a river flowing into the sea, this is Duende.