You generally eat those things really quick in your HC career, and it procs your cheat death (never ever ever leave home without a cheat death in HC, ever, so much stupid shit can one shot you like Enslaved Nightmare Debuff and then bumping into an elite with Jailer/Mortar/Thunderstorm/any other nasty "instant tick affix").

After you cheat death procs, you naturally panic, freak the fuck out, run the opposite way, port to town or run in circles in the cleared map, collect yourself, and run back in when cheat death is not on cooldown anymore.

After a while of doing this, you'll get very good at room clearing (running blind into a room when you knew there were grotesques/molten/arcane) and you'll kind of end up with the habit of popping immunity skills when doing so, or communicating with group (or eating it and proccing cheat death).

After a while you'll proc your cheat death but it'll be so long since you died that you'll feel absolutely invincible and try to rationalize that you won't die (what are the odds something damages you to the point of death 2 times in one minute? That is absurd!), and that type of cavalier attitude you develop will eventually kill you to some really really really dumb shit (I'm talking jumping in guns blazing into the middle of a bunch of Act 1 zombies, and then having no escape, and getting whittled down to nothing, meanwhile thinking "this was dumb as hell, I should not have done this, mistakes were definitely made".

That's pretty much how death in HC works. In HC, you'll generally be running difficulties that you can survive (as opposed to SC where you try to do difficulties that you can merely beat the timer), so the incoming damage is less, but some things can and will one shot you/proc cheat death. After a while it's easy to get lazy and that's what kills you.