He says he'll 'happily' [='gladly'] postpone the appointment.
They have been 'happily' married for 12 years.
We 'happily' accept credit cards.
(..) that she should be with me. You don't have to. I already know I should be with you. And they lived happily ever after. Who? Who did? Oh yes, of course. I remember now. (..)2004 The Notebook