Serenity is a state of soul.
It supercedes any state of mind.
Quotes to consider:
“Serenity is not freedom from the storm, but peace amid the storm.” – Unknown
“God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.” – Reinhold Niebuhr
“Boredom is the feeling that everything is a waste of time; serenity, that nothing is.” – Thomas S. Szasz