Exceptions can always be made like if it's a long time into a gigantic goblin fight and I may lose, maybe I break my rules so I don't have to reload and spend a crapload of time again.
Mostly I don't do anything that gives advantages in combat. No potions, no items, no magic arrows, no scrolls, no dipping, no shoving, no stealth except rogue, no barrelmancy, no poison on weapons, etc.
Also, nothing that doesn't make sense. Wizards can't learn cleric spells, etc.
I only use Laezel's armor if I kill her. Like in my recent run, I failed the deception roll and didn't want to kill the tieflings...so she dies and I take her armor.
And unless MY char dies..they stay dead.
I do sometimes cheat on my "solo runs" and have a full party as pack mules, but they run away and take no actions in combat.