I used to work with a person who was known to most to be a backstabbing, conniving, meddler who would stop at nothing to look good and get promoted. If you weren't "on their side" they would start a campaign against you and could often be seen having whispered conversations in corridors and photocopy rooms. This behind-the- scenes sniping made it very difficult for the targets to respond in any up-front way so it brought out their worst behaviour in return. By the time they left for another job this person had burned many bridges and most people were glad to see the back of them. They had also caused a number of peripheral disputes in the workplace.
I felt like avoiding the after work send-off for this person but forced myself to take the high road and attend. I could tell they were surprised to see me there because we both knew that they had tried to do me a very bad disservice in their own self-interest. Despite that, I sincerely wished them well in the new job. It was like a weight had been lifted from my shoulders by letting go of my grudge. I did regret however that I had allowed myself to be dragged into a couple of the disputes that this person had caused.
What's my point here?
don't be the workplace backstabber/self-promoter. Everyone will know what you are all about and any progress you make up the ladder will be tainted by your legacy of misdeeds.
even when the backstabber makes it really difficult, try to take the high road as much as you can. If you have a legitimate grievance bring it out into the open. Talk to management. It's difficult but try not to retaliate with similar backhanded behaviour. You can't control their behaviour but you can control yours.
don't let them consume you with resentment and anger. It's difficult I know because I was burdened by my grudges for a long time. But, if you find a way to let things go you will feel better in the long run. —Learned my lessons