Well I think when you've lived somewhere all your life, no matter where that is, you can start to see only the negatives and find it a bit boring. There are lots of great things about London - it's diverse and multicultural, there's always stuff going on, the architecture and history is interesting, it's beautiful in places and has some really nice big parks and open green spaces.
When I get frustrated with living here I try to remind myself of the people who visit from other parts of the country (and the rest of the world) and how excited they are to be here.