Boy, that's a tough one for me too. It's gotten better since I've gotten older. I've realized that it's just a fact that we can't all like each other. We're all so different and it usually comes down to chemistry. I used to get totally crushed when I've discovered that someone doesn't like me. Now, I sort of try to look back at our interaction to see if I can identify when that decision was made, etc. I am still always guilty of over-analizing, but that's a different issue!

I've also realized that it is fact that there are people I meet whom I just don't care to associate with again. I don't hate them, I just don't prefer them for whatever reason. Sometimes, I don't even know why. Maybe it's that chemistry thing again.

I'm sure my rambling probably didn't help you one bit. The last thing I would advise is to not give up on people just because you discover one person doesn't care for you. There will be lots more people down the road who do.
Take good care,
Okie