There are different levels of awareness people possess, how they perceive others, and also how others perceive them. Some things are a matter of perception. We cannot continually go around always worrying about offending others or we'd be a neurotic mess. It also requires growing thick skin, or perhaps learning to be tolerant of others.
The longer I exist on this planet the more amazed (and confused) I grow regarding the complexity of human behavior and emotions. We all have a lot to learn about ourselves and others. Be open, do not judge, ask yourself did someone intend to be inconsiderate and hurtful or are they just unaware. It is often hard to give someone feedback without hurting their feelings. How sensitive we all can be.
We all have our issues, and they are different for each one of us. Awareness of what your issues are requires self knowledge; what kinds of things push your buttons. My list is long and I will not go into the details however most recently I seem to allow myself to be bothered most by "know it alls". I actually believe people might not even know when they are behaving that way and no one is likely to tell them, so how are they to know?