For a long time I operated under the frame of mind that if something was bothering me I kept it to myself - well, not so much anymore! I'm trying to do a much better job of letting someone or anyone know when they are getting on my nerves, making me mad or upsetting me. I used to harbor these feelings inside and stew over them, but I figure what does that really do? Nothing. Because then the person doesn't know what they are doing to upset me, therefore they can't fix it - if they want to. Also I usually remember it for much longer and all that accomplishes is to make me continue to be upset or resent that person for something that they didn't even know that they did!
I'm trying not to yell or say mean things, that is not the purpose of "expressing your feelings". What I am try to do is "express" my feelings of hurt, anger, aggravation, in a calm manner before whatever is happening goes too far. Sometimes it works, sometimes it doesn't but more and more I'm getting things off of my chest!