Don't try this at home

Last night:

"It's good to finally have HALO for the PC. And I'm glad I was able to make it through on Normal the first time, rather than chickening out and playing it at Easy. I wonder what Heroic difficulty is like? Hm... I guess I'll try one level - the good old Pillar of Autumn - and find out, before I go to bed."

Four hours (and a few levels and many reloads) later:

"... Uh oh."