The best time to negotiate your salary for a new job is the moment AFTER they say they want you, and not before. Then it becomes a game of chicken for each side to name an amount first, but it is to your advantage to get them to give a number before you do.
The ratio of positive to negative emotions that predicts flourishing is about 3 to 1. Above that ratio, people tend to flourish; below it, they tend to languish.