The best definition of construktive comunication and the difference of negotiation and clash of powers/fight is of the Danish therapist Jesper Juul:
"I talk about myself,
you talk about yourself
this is a constructive negotiation.
I talk about you,
you talk about me,
this is a fight, it's about who is right and who is wrong"
What is the reason / the quality of this statement?
If I talk about myself, my feelings, my likings I talk about facts,- I know them because they're mine. So this is easy to accept for my partner, even if the facts themselves are hard to digest
If I talk about you, I talk about assumptions.
For example if I say: "Your remark .... hurt me," it is a fact, I've been hurt.
If I say:"You hurt me", the partner will understand, that I assume he wanted to hurt me, what isn't necessarily true. May be he wanted to express something totally diffent, and it went wrong. So he is for one instantly on the defence, because he didn't want to do what he means that I'm assuming he wanted to do, and by the way the fact that I've been hurt will vanish behind the quarrel about the assumption.