I'm looking for a word that describes a task or act that you recognise and are accustomed to, but a "familiar task" had a positive colouring which doesn't quite capture what I'm aiming for.
In context, I want the word for a morning ritual which a girl has gone through her entire life, but takes no pleasure in doing so. Specifically, a cold and piercing morning shower to refresh herself.
"For a while, she confides in the familiar, mellow warmth of her bedsheets, but she knows she must get up. Her first choice is the shower, a ___________ that she knows she must do."