***force of habit: a tendency always to do things in a certain way because you have always done them in that way 出于习惯,习惯使然

I don't know why I check all the locks every time I leave the house. It's force of habit, I suppose. 我不知道为什么每次出门都要把所有的门锁检查一遍,我想是出于习惯吧.

***force of circumstance: a situation in which you are forced to do sth by factors beyond your control 迫不得已,情势所逼

He claimed he turned to crime through force of circumstance. He hadn't been able to find a job and his family was starving.他声称自己犯罪是迫不得已.他找不到工作,一家人都在挨饿.

背景音乐:The Fray的Look after you.