This happened to you ... at least once

Like at the police station last time?

I try laughing as hard as I can in my head and that usually helps

I went to an orchestra and then in a very serious moment with low music I laugh. Everyone looked.

I laughed by accident at the movie theater while watching The Help during a particularly sensitive scene and people in front of me were giving me dirty looks after •-•

I laughed during a super important test once. I got 10% off even though it was 100%

All the time....

Why is it that when you're not to laugh under any circumstances, suddenly you feel like laughing at nothing?