“I don't know how you do it.”
You filled in for your coworker while she was out of the office on vacation. You had so much work to do while she was away, and it was difficult for her. Now you have a greater respect for the job she does. You're telling her how hard it was, and you say:
I don't know how you do it.
admiration,
respect,
stative verb,
work 

