"A lifetime of glory is worth a moment of pain." Jack O'Connell may be on the precipice of glory, but the 24-year-old is mindful of the journey ahead. While the British actor has racked up credits and acclaim across the pond (This Is England, Skins, Harry Brown) and drew raves for his turn as a volatile young inmate in this year's award-winning drama Starred Up, this Christmas he tackles his most challenging role yet: Playing American hero Louis Zamperini in Universal's Un…