The shop is only open 'at the whim' of the owner. [=the shop is only open when the owner wants it to be open]
Her husband tries to 'satisfy her every whim'. [=make her happy by doing everything that she wants]
He quit his job 'on a whim'. [=because of a sudden decision]
(..) But you don't really want that. Beatrice... I want you to choose who you truly are and where you truly belong. Not on a whim. Not because you wish you were someone you're not. But because you honestly know yourself. I want you to choose wisely. And I know you will. (..)2014 Divergent