Not to long ago, I was respawning the ender dragon, when something came up, which forced me to leave the game so I could come back later and finish the fight. It turns out that while I was in the pause menu, to leave the game, the dragon shot a fireball at me (the ones that have the purple radius around the landing of the fireball that deal damage to the player until the player is outside of it or dead). When I was loading, leaving, and even still in the pause menu, the game never paused, like it should have, it did by the time I was in the menu, but it was still enough time to go through full health and a Totem of Undying. I think that the Survival Community would all be helped greatly if you:

A.) Made the pause menu pause the game

B.) Fixed thebug where the world would continue on, despite the player having had already left the game

C.) Fixed the bug where the world would load faster than the player into the world would