One has to draw the line somewhere
(one) has to draw a/the line somewhere
There is an inevitable certain threshold that one must set and enforce beyond which no further acceptance, compromise, or cooperation is acceptable. Why do you keep letting your boss pile on more and more work like that? You have to draw the line somewhere! They just kept demanding changes to our deal, until I finally told them I was out. I had to draw a line somewhere. How much longer will we keep letting them take advantage of us? We've got to draw a line somewhere!
One has to draw the line somewhere.
Prov. It is necessary to set limits and enforce them. Ellen: This is the fifth night this week that my son has stayed out too late. Jane: Why not punish him, then? You have to draw the line somewhere. I am a fairly easygoing employer, but I cannot allow my employees to take two hours for lunch. I have to draw the line somewhere.