忙于工作的英文：
be at it

I hate to interrupt a man when he's busy working.
＂一个人忙于工作时,我最不愿打搅了。＂

As everyone is busy at his or her work usually, the people would gradually be estranged from each other.
平时，大家都忙于工作，人和人之间关系也会慢慢地疏远。