..the way to think about these things has less to do with the invulnerability promoted by the official doctrines, and more to do with, one might say, using these doctrines to take the edge off of vulnerability, to allow one to experience life without becoming overwhelmed or depressed or resentful or bitter, except perhaps at the extremity of loss. There is some combination of embedding oneself in the world in a vulnerable way and not being completely undone by that vulnerability that is pointed at, if not directly endorsed, by the official doctrines.
It seems to me that Taoism, Buddhism, Stoicism, etc. work not by making one invulnerable but rather by allowing one to step back from the immediacy of the situation so that the experience of pain or suffering is seen for what it is, precisely as part of a contingent process, a process that could have yielded a very different present but just happened to yield this one.Another point would be the evolution of our social brain has resulted in a built in bias towards feeling the sort of vulnerability and bonding that sustains and defends social group identity. A group of floating detached Taoists isn't all that useful in intergroup conflicts. Finally, disciplines that result in maintaining emotional distance from others can also let atrophy the evolved neuroendocrine chemistries that can vitalize our physiology and longevity.