Crying until you can't breathe, holding onto each other and crying until you laugh.
Late-night scary movies that make you jump and laugh, then when the nightmare wakes you in the predawn hours, it is reaching over to feel someone breathing and knowing that you are safe.
Listening to someone's anger, knowing it has nothing at all to do with you, giving them space to find their way back again and when they do, telling them that you love them no matter what and everything will be alright.
Road trips and making getting lost an unexpected adventure.
Comfortable silences that are only broken when both of you say almost the same exact thing.
Laughter. Always laughter.