by force of habit
US /baɪ fɔrs əv ˈhæbɪt/
UK /baɪ fɔrs əv ˈhæbɪt/

1.
出於習慣, 習慣使然
because of a routine or custom, without conscious thought
:
•
He still checks his old email account every morning by force of habit.
他每天早上仍然出於習慣檢查他的舊電子郵件帳戶。
•
She automatically reached for her phone by force of habit, even though she knew it was dead.
她出於習慣自動伸手去拿手機,儘管她知道手機沒電了。