How we change what others think, feel, believe and do
When another person makes a statement with which you disagree, state that you disagree with them, rather than appearing to agree. Even if you passively say nothing, you have, in effect, agreed with them.
Make the fact that you disagree clear.
You can soften the impact by appreciating how the other person may be mistaken, but do not let this weaken your disagreement.
If you have a contrary view, then follow up your disagreement by stating this view. Where possible, be constructive, helping them see a way forward from any embarrassment.
If appropriate, listen to their response, and be prepared to change your own view if what they say makes sense. Never change because of fears or threats.
If you do not want to discuss the matter further, then say so.
Do not be drawn into a destructive argument. If they become emotional or aggressive, stay cool and do not give in just to calm them down.
Reward them for a good response to your disagreement with a smile or other accepting behavior or language.
John, I think you're wrong. If you do that then you will add risk to the schedule. We cannot do this in less than a month.
That's not true. I was there last week and saw it with my own eyes.
I can see how that may appear to be so, but I spoke with Sam today and she told me that she was not there. We could try speaking with Susan.
Disagreeing can be a very difficult thing for people who do not yet find assertion an easy task. Even more than saying no, it risks disapproval and social punishment. If you are drawn into an argument, you may fear being proven wrong.
A constructive argument is a good test of your assertiveness and assertive beliefs, as it will require you to stay positive and rational whilst handling the other person's varying behavior.
If emotions are aroused and a discussion turns into a heated argument, then rationality will be lost. Giving in to other people when their emotions are aroused is teaching them that the best way to persuade you is to become emotional.