You know, I was thinking... is the XP pool necessary? I was thinking you could probably eliminate it entirely, and just have skills train through use to a degree correlated to your morale, sort of eliminating the middleman. I can't think of a drawback to this, especially since you tend to get too much XP to use anyway currently.
Something about this is actually planned to change, at least. I do think that the method we have now might not be the best, and at the very least it needs balancing and tweaking, but I'm not sure if a direct Mood->Skill Boost (which is what I think is being considered as the main alternative) is the best route either, considering the volatility.
I have my own ideas about this, though - I'll probably write them up in more detail later, but here's a brief explanation of what I'd like to see:
I'd essentially change the current "morale" to "mood", which is more reflective anyways, and have it influence (but not necessarily control) a "morale" value that fluctuates between -200 and +200, with -100 representing zero skill growth, +100 representing double skill growth (and 200 quad), and -200 meaning your character has lost the will to live and runs a risk of committing suicide.
Mood would governs things like elated, and have most of the current morale effects plus modifiers for pain and the like, and a positive or negative mood steadily influences morale (with diminishing returns for moods of the same value as the morale dips deep or climbs higher). It wouldn't be the only thing, though. Some effects, such as days of bland food and bad water, wouldn't do much about a character's current mood (which could be blissfully drugged out of his mind ), but would affect how he's framing his goals and options and potential (his actual morale). Some traits, like optimism, would effect morale directly. Over time, the player would have other traits like loneliness and boredom which can develop and steadily get worse, giving an actual difficulty curve over time, where the game gets harder and you need to go further out of your way to keep the morale up - and a single night of drinking isn't going to be enough to leave you back in tip-top shape.