No one really ever asked (Han did), but if they were to ("Why don't you let yourself live a little, Princess") first she would flinch because it violated her list. Do Not Remember headed it, and it was followed by No Self-Pity and Win the War. If they asked, ("Why not- it'll warm you up"), she would deliver an icy stare, for Do Not Reveal Emotion held a prominent position, but if someone persisted ("for kriff's sake- it's kaf!") she might try to explain that it was a form of solidarity with her people and planet.
("But- they're dead.")
If it was true the best way to get a pass on hell in the afterlife was to live one's life punishingly, then Leia figured she was scoring extra points on Hoth. Everyone suffered, but none so gamely as Princess Leia of Alderaan. She hadn't thought of Physical Discomfort for her list, but took to it with an almost savage enjoyment.
Her feet were so cold it felt like her legs ended at the top of her ankle. Her nose threatened to drop the same drip for eternity but never did. She ripped off hangnails that formed when the rough glove material scraped the dry skin of her hands, and her neck and shoulders ached from holding herself in a constant shiver.
Bathing, however, was permitted. One's bare skin had to be exposed to the cold, which, oh, made one's teeth grit. Sleep and the occasional tasteless meal (Ingest Without Enjoyment) were allowed, because depriving herself of these would only result in a faint, and Do Not Call Attention to Yourself was also important.
She allowed herself to like Luke. Everyone knew by now it was he who was inspired to rescue her from the Death Star, and she honored his own struggles.
Luxury, of course, was forbidden. Joy was out, as was fun. Her quarters were spartan. There were no personal effects: no holos, no trinkets. Only her uniform, and the bed and blanket provided by the Alliance. Han Solo had developed a brisk trade on Hoth, bringing back useful items in bulk in addition to his smuggling duties, and most had purchased a heater for their own quarters. General Rieekan's response, when Leia encouraged shutting Solo's storefront down (No Contraband) had been to purchase two.
She did give herself permission, however, to resent, and her special target went by the name of Han Solo. This was almost an indulgence, as he made it so easy. He provided so many opportunities it was almost as if he did it on purpose.
Sometimes it bordered on fun, so she had to be careful. Or he caused her to risk breaking the Arguments section of her own self-imposed rule of Do Not Lose (this included not only arguments, but battles and lives). She would forbid herself contact with him- difficult to do on the tiny, frozen base of Hoth- and think, and remember, and return to a diet of emotional deprivation.
She resented, most famously, that he had not properly joined the Rebellion. "You've known me how many years?" he'd ask when she brought it up.
Luke would provide the answer. Of course since it was the most historical of her resentment, the answer changed. "Going on a few months," he supplied helpfully earlier in their acquaintance. Later on, with brows raised, surprised at the answer, he exclaimed, "Two!", and most recently, resigned and tired of the argument, he would sigh heavily, "Three."
What Han Solo meant when he asked how long she knew knew him- and he would never say it, and she didn't know why, because she could resent that, too- "Three years sounds like I'm committed to something."
What else was there other than the Rebellion? She dared not let herself think of it.
It wasn't just his stubborn independence she resented. It was how well he seemed to do in the cold, that General Rieekan liked him; she resented, his ship, his good looks, his Life Debt because it meant he had once acted heroically but he wouldn't do it anymore.
Except, he did. Not just on the Death Star, but three years later, when she raised the alert too late and he went to find where Luke was.
It was her list, gods damn it. He needed to stay off it. Do Not Lose. Do Not Love.