Once upon a time when I was younger, dumber and definitely more rash in my decision making, I had an ISSUE with someone I worked with. She had an ISSUE with me too and neither one of us handled it well. It wasn't like we had an all out chick fight on the floor or anything but it quickly became petty, with shit talking and squabbling.
It even got to the point that we both had to go to HR about it. She eventually ended up getting fired for essentially not doing her job (which quite honestly was one of the problems that I had with her, but I handled it very poorly) It was definitely not my finest hour.
That moment, at age 20-something was THE MOMENT. The moment where I realized I could seriously fuck up my career and my potential to have a better career if I didn't get my shit together. I learned that it wasn't that I couldn't have problems with others, or that I couldn't say something if shit was wrong but it was all in HOW you did things, HOW you said things. It really is all in the delivery.
It took a me a long time to figure out how to deal with these kinds of issues and I still don't always get it right but I do know better now. Don't talk shit about people at work. If you have a problem with someone, try and talk to them about it, if you can't talk to them, talk to management, talk to HR but DON'T be child about it. It's a hard lesson to learn, especially the shit talking bit. It's so easy to slip into old patterns and to find yourself talking shit without even realizing it. It's okay to complain a bit about something that is bugging you, but it's another thing to say "god x is so stupid" or "I hate x". I know I catch myself doing it once in awhile and I am still doing my damndest to not be that person.
But really the only real way to succeed is to learn how to deal with people you may not like or get along with. You need to learn how to work with people who work differently or slower than you do. Learning these things will do nothing but help you in the long run.
So keep calm, take a deep breath and try to let it go, or if you can't let it go, take it to the appropriate people. It'll help you. Trust me on this.