We always argue, but we always laugh. Is that normal?

I'm May 9 1988. A female. My girlfriend is October 8 1990. I was born at 9AM she was born at 6PM.
I've never been with a horse in my life. Ive been with a snake and a pig and a sheep. But Non of them last. We have been together Four years now. But we always argue all the time it gets really tiring and exhausting. But, I have never met someone who makes me laugh more than her. So actually its so hard to stay mad at her? Is this normal? Are we meant to be? Or is it true what the zodiac says that we are just love at first sight??