If they are your real friends, they will realize it and stop doing it. If you have people in your life that constantly do it even though they see that its making you feel bad or somehow affecting you negatively, the best thing to do is to part ways. That's what I have been doing so far and continue to do so. You shouldn't tolerate negative people in your life because even if you life is good, they will make sure you feel that it isn't that good actually.