I wonder why bed-time brings serenity. Retrospecting on the events of the day is the most common thing the one finds oneself in. The calmness of the night at the end of the day allows you to contemplate life more clearly. Thoughts are more free-flowing. It may be because of the silence around. Silence is very soothing, even joyful at times, specially when you are constantly always listening to something: noise, music, chatter, buzz, horns, throughout the day. The silence of the night takes you away from all this clutter and fills you with tranquility.
In such silence, the thoughts are profoundly clear. You can find the most satisfying answers to some of the most perplexing questions. An idea suddenly occurs. A plan formulates. Hope usurps. Fears quietened. A favourite song, long forgotten, comes to the lips. The mind rests. The heart then takes over. Such a state is the most peaceful. Then sleep descends.