How do I handle disagreements?

When I disagree with people I don't handle it very well.  I feel as if I'm right and there is no way that what they are saying is right.  For example, my friend and I were disagreeing on the correct way to say catch.  I say catch with the  a sounding the same as it would in latch.  My friend says catch sounding like ketch.  We kept arguing but not like angry arguing, with both thought the other was stupid for saying it like that.  We got to the point where we couldn't stop laughing and we were almost yelling at eachother, but still not mad at eachother at all.  She definitely has the better makings of a lawyer than I do!