By-Two Kaapi in an oilfield

Wonder why we get pissed at others for reasons galore.

Getting pissed at -
The instructor for not giving 4 more marks
The chat stall owner for not extending credit
A classmate for maxing a test and increasing the class average
A friend for refusing to come to a party
Some jerk for trying to hit upon some friends

Am just pondering over the arguement that I shouldn't get pissed at these.
The reason being that

At all times, every man acts according to his priorities and for his rational self-interest. So, what is wrong in any of his actions due to which you get pissed ?!

If objectivism is the way to be, then my friend did not want to come to the party because of his/her priorities and rational self-interest. So, why on sweet Earth should I be mad at him/her? Ergo, there is no point in me being pissed at either my instructor or the chat stall owner or that jerk. It's just about accepting people the way they are and living life on your terms.

Whatever! Guess, I shall ponder over Ayn Rand's quote:

I swear by my life and my love of it that I will never live for the sake of another man, nor ask another man to live for mine