Give someone an inch and he’ll (she’ll) take a yard 小人得寸便進尺

米德佳提供中文到英文翻譯服務，含英文編修

Be generous to someone and the person will demand even more. (Describes someone who will take advantage of you if you are even a little kind to him or her).

Examples

“I’m always wary about making concessions with these people. Give them an inch and they’ll take a mile.”

“If you let Mark borrow your tools for this weekend, he’ll wind up keeping them for years. Give an inch and he’ll take a mile. ”