According to Wikipedia:
Il bicchiere della staffa è l’ultimo bicchiere che si beve prima di congedarsi dagli amici, in genere per recarsi a casa propria per riposare.
Si ritiene che l’espressione sia nata nell’Ottocento, quando i signori che si recavano nelle locande bevevano l’ultimo bicchiere quando già avevano un piede nella staffa, pronti per montare a cavallo.
which I would roughly translate as:
‘Il bicchiere della staffa’ (‘one for the road’) is the glass that you drink before saying goodbye to your friends, usually to head home to sleep.
It’s said that the expression originated in the ninteenth century, when those who frequented drinking establishments would have a final glass when they already had one foot in the stirrup, ready to mount their horses.
Today’s new, free material for students of Italian is, you guessed, ‘Il bicchiere‘.
As in ‘vedo il bicchiere mezzo vuoto’.
For me, the glass is usually half-empty, I was brought up that way.
As my dear mother used to say, when frowning over my school reports, “Far better to expect the worst, then you won’t get any unpleasant surprises!”
What about you?
Language learners tend to be optimists, ‘bicchiere mezzo pieno’ people.
You have to be, beginning such an enormous undertaking as learning a new language.
It might, after all, take you the rest of your life.
Perhaps not even then?
Still, if the glass is half-full…
Look what progress you’ve made already.
Once, you couldn’t even say ‘Ciao’.
Yet now, you sing ‘Bella Ciao!’ in the shower.
Better learn, then.
Check out this version with English subtitles, to get the general idea.
And then this rather ‘stuck up’ one, which has the full lyrics in Italian for you to memorise (the comments are worth a look, too.)
So, one for the road?