Why do Christians try to force their religion on others?

I mean with missionaries, even though they do good work, they pay people to convert, they trick them, they divide communities, breaks families, cause tension, why can't they mind their own business, if you want to feed people, by all mean go ahead. But why do they insist that they CONVERT before feeding you. Why do they tell new converts to hate their former religion, and the religion of their parents. I was working with this lady, when she found out I wasn't Christian, she started leaving passages of the bible on my desk, and talked about how bad hell is, and how I'm going there. Is it too much to ask to mind your own business, I'm fine with who I am. I hate when street preachers scream into peoples faces, that Christ will have no mercy for non-believers. I'm fine with Christians believing in what they want, but why not let me live life alone? Can someone tell me why, so many of them do this, I don't think they are bad people, but why...?