Very true! In most cases, it's borderline subconscious with much unintentionality to it. I've come across the familiar experience of asking oneself "what the hell you've just done?" after the act is over and I'm back in this thing we call 'normal mind'.
The feeling of unfairness is usually much worse as it creates the feeling of getting back at the other party in one way or another to make things fair. The goal is always to create a win-win situation where each party walks away feeling that they've gained something. Sometimes, this could mean purposely leaving money on the table.
Thanks for the kind remarks and for stopping by :)