Negative numbers are just like the positive ones, but kind of... the opposite. Like the indentation formed if you pressed the positive number into clay or sand or something. It's like they want to be filled or take away from something else rather than adding onto other forms.

RE how I think about imaginary or complex numbers, in short, I don't :)

I've never studied much higher math, and don't have any reason to think that I'd be particularly good at it.