Picture that person that you are so angry with standing there with the most ridiculous pair of underwear you have ever seen. Make it so ridiculous that it almost makes you laugh. Really see. Concentrate on that and that alone. When it works the first time you will laugh. That really makes people wonder what on earth is wrong with you. But who cares? You've turned an ugly situation into one that makes you smile or laugh. Give it a try...it can't hurt:)
And remember to pick your battles in life. Few things are really worth getting upset over. If it won't matter in a year from now, or a month or next week, let it go. It just doesn't matter.