Serenity is lying next to someone at night.
Feeling the heat from their body, even if we don't touch.
Hearing the small sounds that announce their presence -- breathing, a muffled cough, the creak of springs as they turn over.
Smelling their sweat, or their soap, their shampoo, or the perfume they wear.
Seeing the shape under the bedclothes that means I am not alone.
Knowing that, if I have a nightmare, they will hold me, and comfort me; and that, if I want to, I can stretch out and caress them, kiss them, make love to them.
Feeling, seeing, hearing, smelling, knowing that someone is there.