Don’t ever, ever, ever, ever negotiate. It’s a statement, that in effect, you were trying to get more but will settle for less.
Instead, change the terms. Reduce the offering, increase the deliverable, or if necessary, restart the sales process so you can communicate your value.
It’s simple. Your integrity is more important than your margin. If you can’t justify the value, don’t start dropping the price. Unless you sell a commodity you will lose, every time…