it was said in a simple way; when you're sad cry. - like

it was said in a simple way;
when you're sad cry.
- like when you're happy and you can't help but laugh.
in the same way, when you're sad and it can't be helped, thoughtlessly wtih no restraint just as easily as you once laughed, you can cry too.
holding back a laugh never made the situation less funny anyways.