Offense, Drama, DTR, and the likes

I wish I could say what I feel and not have the other person be offended. I am talking about any kind of relationship--dating, sibling, friends, etc. And it isn't limited to whether they take offense, it is also the fact that I do not express my feelings and in the end I feel far away. Sometimes I let silly things bother me so I just let them stew over time and they go away eventually but I would feel lot better if I had spoken to someone about it. In my experiences of telling the person who has hurt me, I feel worse after telling them because I alone would rather feel those negative emotions and just forget about it. I look at the relationships I have right now, and they are so awesome and fun! I really love my friends and family. But every now and then things are hard and I just try and truck on through it without really expressing any concern about it. It is important to me that the other person is happy and feels the least pain as possible--no DTR, no drama. But if there is only happiness can we truly call it happiness? If there wasn't an opposite--a relationship with no pain and sorrow--then aren't we cutting short the greatest amount of joy we could feel? Man, I don't know where to even start to be better at this.