When a statement or a joke amuses you to a point, to an extent which would fill you with warmth and make you grin broadly, but not necessarily laugh. It gets you in a personal place. Perhaps it appeals to nostalgia, or it's simply a joke that only you find funny, or particularly resonates with you for no apparent reason.

when you're hungover as shit after a spending a night drunk as a skunk

to insert a finger into the anus

When you bust a fat nut after you Beat Your Meat