Big things like greed, corruption, discrimination, poverty, abuse, the environment and so on.
Things (perhaps perceived to be more trivial) like the state of the England football team, people saying you have no sense of humour (we all have one, it's just different to yours), things becoming more and more expensive, inside jokes, people associating you not drinking as much as them as anti-social/someone who doesn't get out much...
The list goes on for both of those really.
Is it worth going? Find out here