Existence precedes essence or is it the other way around?

Last class we touched upon the philosophical notion of existence preceding essence. When I was a senior in high school, I was obsessed with the idea that we have no pre-defined existence. My obsession with existentialism and this notion in particular all began when I read existentialism is a humanism by Jean-Paul Sartre. After reading this work, I thought to my self :"Yes, yes, we are nothing until we become! I have no purpose until I create it for myself!" For a good long while I dismissed the possibility of a god, a soul, a destiny or purpose. You might even say I was a borderline nihilist. I believed in nothing except action. This of course all changed when I became re-acquainted with my artistic soul. I remember the day I came to New Orleans. I felt something within me awaken. It was then I wrote without choice what I consider my first inspired song, a song stemming from a place beyond myself. Gradually I began to re-evaluate my staunch opinions on existence and began to think "I am not writing my songs, they are writing me". Since my awakening, someone or something much greater than myself compels me to create. For this reason, among others (which if I were to get into, fellow bloggers might think me quite strange) I now believe essence precedes existence. In other words the call comes before the action. I never dreamed of becoming a songwriter. I did not mould myself out of nothing to become a songwriter. I am a songwriter by my very nature, my very essence.