Discipline yourself not to provide quick responses. When the other side makes a demand or offer, be it acceptable or not, don’t respond to it with a quick “yes” or “no.” Just keep quiet and think about it for a while. Better yet, write down a few calculations that only you can see or ask for some time to do a little research. Then when you do provide an answer, be it a “yes” or “no,” or anything else, your considered response will give greater weight to your answer. Whatever it is. A considered response gives your answer more credibility and respect. It becomes a stronger “no.”