Friends - Is this how it works? And a question about hate

I've re-introduced myself into society after a long period of seclusion.
And I don't really have anyone to ask so you lot are the best I've got!

The two questions are:

1. How come the few people I really disliked at first became my closets friends?

Where this question comes from -

I work in a high stress environment that requires lots of costumer service face to face and on the phone, as I figured it will give me the experience I need to get used to people again.

On the job I got to know several different kinds of people, be it "fleeting" costumers or people I have to deal with daily.

And after several months I noticed that people I didn't like at first from the people I deal with daily are the people I trust most and have fun with the most. It really turned around.

So I was curious about your experiences and opinions on the matter, should I, from now on, just look for people who annoy me when I first meet them because I can assume we'll be pals in a few weeks? x)

2. How easily hate is built?

Where this question comes from -

I promised myself to be as honest and open as I can in this trail run of a journey I took myself into so I can really learn how to handle people by being who I am.

And I think that resulted in some people disliking me, which is fine I figured that will happen - but am I selling them short? I feel like every time someone is mad at me, especially if they show signs more than once, our relationship is ruined forever.

Is it ever like that?

I know I shouldn't do it but I can't help comparing how those who I think dislike me treat some other people versus how they treat me. And when I see how nice they are to these people I start to think it's a lost cause and I should dismiss them and be done with it.

Thanks for the help!

Have a nice life, you deserve it!