I often write about this, because it is a constant concern, and it helps to write about it. I am very conscious of every noise my upstairs neighbour makes, from walking above me, to using the taps. And when there is no noise, I worry about when the next intrusion will be. I can hear her voice, shouting at her dog (not that often, but it shakes me when it happens), and I worry about whether she can hear my noise and music, which is pretty quiet. It means I can't relax fully in my own home.
I am also very privacy conscious, and can't use my private back garden because the fence is too low; the neighbour peers over it and tries to talk to me, so I just avoid going out the back. I am hoping to raise the fence to 6 feet soon, which should help, but currently I can't care for the garden. Despite having net curtains, and knowing rationally that the neighbour can't see inside my kitchen, I also feel on edge when I see the neighbour in the garden - she seems so close to me.
I have OCD and wash up a lot - what if I annoy her with having my tap on all the time, and will she seek revenge if she can hear me? I know this sounds paraonid, but I worry that if she can hear my noise, she will create louder noise that I will have to endure.
Cars constantly drive past my flat, and some of them are very loud. I go to sleep with my fingers in my ears. This is very uncomfortable, but prevents the noise anxiety. I often wake up tired, though, and have to catch up on sleep at my parents. Their house is not the quietest of places, and I get woken up at 5am by my brother coming back from night shift, but I sleep better there than at my flat. At least I can't hear any cars or a neighbour's footsteps above my head - they live in a semi-detached, set back from the road.
So no privacy, constant awareness of neighbour's every move, and a sense of being watched.
maybe that is the KEY 
I Like the sound of the that 
