We all come across people in our life that always seem to do nothing but complain. Maybe most of them do not even realize they are being negative & would love a little reminder that their positivity is lacking.
Right after they finish complaining, say to them, "Now tell me something positive" Some people have no idea how negative they have become. That is what they surround themselves with, day in and day out, so it is just a way of life for them. Being given a reminder, they may realize that is not how they want to project and start working on becoming more positive.
Just my thoughts.