take (something) sitting down
To accept something unpleasant, unfortunate, or unjust without resistance, argument, or action. (Usually used in the negative to express the opposite.) I just found out my wife has been cheating on me for the last year, and I'm not about to take it sitting down! I've been at this job for nearly 30 years and not once have I been given a raise. If you think I'm going to take it sitting down any longer, then you have another think coming!