Say no, then negotiate.
- Helga's Rule

Your negotiations may lead to either a victory or a loss. The shame of your loss in a private negotiating session may be compounded if you have to report the conclusion to another person.

Although other parties will inevitably be curious about the circumstances, do refrain from explanations.

Any reasons that you proffer will have a taste of sour grapes. In some cases, they will have to be presented in a negative way. That may involve lashon hara, or castigating your negotiating partner.

After all, it is difficult to blame yourself for losing the negotiations. It is also difficult for you to report on any negative issue raised by your negotiating partner in a fair manner.

Avoid the problems by refraining from giving reasons. In that way, you will avoid the concomitant issues that may arise.