"Jumping Into The Sky" by Samantha Murray appeared in Daily Science Fiction on June 10, 2013. "A fifteen-year-old boy receives a jar of invulnerability cream as a gift from his gran."
"Invulnerable" means something like being impervious to injury. The term is mainly used to mean physical invulnerability, but the word could also mean imperviousness to emotional pain. Ms. Murray does a nice exploration of the nuanced meaning of invulnerability in her charming story. 5 out of 7 rocket-dragons.