by force of habit
US /baɪ fɔrs əv ˈhæbɪt/
UK /baɪ fɔrs əv ˈhæbɪt/
1.
because of a routine or custom, without conscious thought
:
•
He still checks his old email account every morning by force of habit.
•
She automatically reached for her phone by force of habit, even though she knew it was dead.