How Can I Stop My Affair With My Neighbour?

I live and work in one of the cities in Southwest Nigeria. I'm single, male with a female working class neighbour who is also single. For some months now, we've been seeing each other and it's now driving me nuts. It's clear than we can't date talk more of getting married. Our romance started sometimes mid last year after we spent some time gisting in my apartment and has continued since then. I have tried to keep away from her but after a month at most, we come back together. She has started to fall in love with me and I've got to stop this as soon as possible. I need advice please.