Some Like It Hot: as consoling as a lullaby.
I once heard about a mental hospital where all the televisions were permanently tuned to ITV. The reasoning was that the other channels might occasionally toss in a disturbing documentary or challenging drama, whereas ITV - with its soothing diet of Richard and Judy, Des O'Connor and Heartbeat reruns - was deemed less likely to spook the patients.
I adopt a similar policy when it comes to hangovers. When sober, my viewing tastes are reasonably eclectic. When drunk, I'll watch pretty much anything, safe in the knowledge that I probably won't remember it the next day. But the hungover me is fragile, conservative and easily upset. At such times only the finest comfort viewing will do.
These, then, are the hangover movies that work for me. They are all good - or at least good-ish - films, but they also possess a certain comforting quality, either as a result of their subject matter or their familiarity (or both).
Comedies are generally a safe bet, so long as they're not too raucous. You're better off sticking to Ealing classics like The Ladykillers or Kind Hearts and Coronets, or some of the gentler screwballs (The Awful Truth, Holiday). The Philadelphia Story and Harvey both have a certain airy grace (and both, coincidentally, feature James Stewart as a loveable drunk). And I've watched Some Like it Hot so many times that its harum-scarum rhythms are now as consoling as a lullaby.
Westerns also work well. Steer clear of the overheated spaghetti romps and the Sam Peckinpah splatter-fests and plump for some solid, leisurely old faithful like Red River or My Darling Clementine. Thrillers contain thrills and must be avoided. Musicals tend to be relentlessly cheerful and are likewise to be handled with care, although I'll make an exception for Meet Me in St Louis. Amiable dramas like Breaking Away can be a tonic, and I once nursed a horrible Christmas hangover through the entire run of Ben-Hur, gliding from slave-ship to amphitheatre to leper colony as the headache slowly faded. For that reason alone, it has earned its place in the canon (not the loud sort of canon; the quiet kind).
Please be advised that these are not hangover cures, just hangover accompaniments. Misery needs company, and films are as good a way as any to fill the painful spells before sickness stops and the drinking can start again.
