I'm working with a Co worker who is doing my head in. He keeps talking about being old, about how it's too late to expect to achieve anything, about how all the younger people in the team are bright and entrepreneurial (they definitely are not) and wanted me to agree with him that my teeth were getting loose (they aren't) how can I handle this without telling him to fuck off.. He doesn't get the subject- changing, diversion tactics I use..I find it really odd and depressing to divide the team up by age and it's hard to join in an 'everything is shit' conversation.. Help!