Expectations

Why do people get in conflicts and disagreements, get angry on each other, no matter if it's work, personal life or friends? I thought today that it's cuz each one of us has certain expectations towards our team or particular person. We expect people around to act according to what's on our mind, often not telling it to them, but only blaming afterwards, if it's not done the way we were expecting. But is it possible not to have expectations towards smth? Or maybe key to find common solution is setting up expectations from the beginning? 

Another thing I noticed even in myself is that often we get trapped by expectations of other people toward us. My family is expecting my to finish with AIESEC this year, move to Almaty and start working, my AIESEC friends expect that one more year I'll be around and continue working in our organization. And you try to manage these expectations, but in the end somebody will stay dissapointed with decision you took. And I myself tend to get frustrated when something doesn't match the way I was expecting, even in small things. I like this saying: "If person doesn't love you the way you expect, it does not mean he doesn't love you at all.". So at least for myself I decided to be aware of this and differences with other people, not to get angry if smth not the way you want, but trying to understand other's thoughts and come to common solution.