Probably unnecessary back up to the point about grief and laughter but after I suffered the loss of someone very close I did a lot of crying and all the conventional responses but my god in the following 6 months I laughed like I don't think I ever have before or since. There's something very elemental about powerful emotions it's like they all blur into one, that's how it was for me. Also there's a sense that the mask slips - I couldn't conceal what I was feeling - at all, so if I suddenly remembered something funny, I'd laugh and I couldn't not laugh. I remember doing this on the underground and the reactions of everyone around me were so weird that it made me laugh even harder, I was nearly crying with laughter by the time I got off. Proper nutcase style. Luckily it was the Victoria line down to Brixton so I passed for a local.