To summarize my response to the OP's title question: Yes, being nice to others will pay off in the long run. Sending positive energy out in the world increases the chance that positive energy will come back to us. Though that is not to say that being pleasant will suddenly change our life into the one we want....that takes a lot of work on the self. The reverse is also true....being unpleasant and judgmental increases the risk of being surrounded by unpleasantness or being avoided. A negative attribution bias can convince a person that people are horrible even when they aren't. And as I said, being pleasant does not mean we have to give people our money or forget our boundaries.