Keep it in.

You hear a noise, and realise your sister could easily hear you. This was all her fault, and you know it. You couldn't give her the satisfaction. You don't have proof, but it must have been some kind of cruel prank. She was often like that.

You slip on a pair of pajama pants in hopes that it stops your wandering hand, and you curl into bed. Your body is still burning hot, and it takes hours and every bit of your concentration to avoid giving into temptation. You know that come morning, the sensation will have died down, so all you need to do is fall asleep.

Eventually, you do.