Here's a simple explanation:
- positive $\times$ positive: If a good thing happens to a good person, that's good! :)
- negative $\times$ positive: If a bad thing happends to a good person, that's bad. :(
- positive $\times$ negative: If a good thing happens to a bad person, that's also bad. :(
- negative $\times$ negative: But, if a bad thing happens to a bad person, that's good!! :)
If you don't think this funny, then you're just wrongyou are simply mistaken: https://www.youtube.com/watch?v=YbM1xFvzcvA