Having been given strict education at a young age, even though Gerald would not decline any offered in social events amongst nobles, he was strictly prohibited from losing himself in such enjoyments that paralyzes the spirit.
As a personal guard serving the mayor of Lancaster, Gerald had relatively strong self-discipline and would keep himself to short sips despite his fondness for alcohol.
Still, today's circumstances were special: the feasts held by the Players who were born as the dregs of society were not as cagey as the banquets of noble families. Even if they did not sink to the level of debauchery, there was still a considerable lack of restraint.
Hence, affected by the Players, Gerald—who had been drinking away his troubles—couldn't help breaking his usual alcohol limit.