Apart from the obvious (weather etc), it's even hard to say. The city just feels harsh to me. One of the things that I first noticed when I moved here was how it's uncommon to find places to sit when you're out and about. If you're out all day you can't just sit in some bench and rest a bit because they're virtually non-existent. You have to go into a coffee shop. I think it's loads of tiny things like that.

Maybe that wasn't very convincing...

EDIT: Of course also the rents. I'm lucky enough that I have big windows to the park, but I'm paying an absurd fortune. The alternative is moving to the periphery where I have to spend 1 hour on the tube each way and when I go home I'm worring that I'm gonna get stabbed.