Poor John's been putting on a brave face so far in these stories. Something had to crack, and fortunately it was the ship and not his mind or his spirit. Holmes will get him good and drunk and let him rip and swear all he likes. The next day Watson will have a ghastly hangover which will distract him from his mental pain, and he'll go right back to making his way around the cottage and stowing his self-pity away.