So much has come before those battles lost and won

Yeah. (Unless you want to play fate/something verse with me, in which case this still applies but there is BONUS headcanon.)

So, the Epic of Gilgamesh. If you haven't read it, you should. If you don't feel like reading tedious translated versions of really really really old tablets, or the more easily readable versions floating about, that's still fine. Just read the BetterMyths version. It'll be easier, take less time, and still get the point across. And you'll laugh a lot, or at least I did.