Negotiation skills can help you. The aim of win-win negotiation is to find a solution that is acceptable to both parties.
There are different styles of negotiation, depending on circumstances.
Where you do not expect to deal with people ever again and you do not need their goodwill e.g. buy or sell a house.
When there is a great deal at stake in a negotiation, then it may be appropriate to behave in 'gamesmanship' to gain advantage. Anyone who has been involved with large sales negotiations will be familiar with this. This approach is not good for resolving disputes with people with whom you have an ongoing relationship: Similarly, using tricks and manipulation during a negotiation can undermine trust and damage teamwork. Here, honesty and openness are almost always the best policies.
Depending on the scale of the disagreement, some preparation may be appropriate for conducting a successful negotiation. it should strengthens your position, it should not weaken the other person's.
However, if you need to resolve a major disagreement, then make sure you prepare thoroughly. Some of the points you should consider like:-
What do you want to get out of the negotiation? What do you think the other person wants? What level is comfortable giving away? What other alternatives do you have? Does failure to reach an agreement cut you out of future opportunities? And what alternatives might the other person have? What is the history of the relationship? What are precedents set before? What are the consequences for you of winning or losing this negotiation? Who has what power in the relationship? Etc.. Etc...
For a negotiation to be 'win-win', both parties should feel positive about the negotiation once it's over. This helps people keep good working relationships afterwards.
Emotion can be an important subject of discussion because people's emotional needs must fairly be met. Be as detached as possible when discussing your own emotions - perhaps discuss them as if emotions belong to someone else.
In an ideal situation, you will find that the other person wants what you are prepared to trade, and that you are prepared to give what the other person wants.
If this is not the case and one person must give way, then it is fair for this person to try to negotiate some form of compensation. Ultimately, both sides should feel comfortable with the final solution if the agreement is to be considered win-win.