How to be free from attachment, but principled

Recently I was wondering if I should pursue a matter or just let it go as what many of my acquaintances asked me to. 

After watching this video, I know the decision I made is right as it is the right thing to do. 

What is the difference between attachment and adhering to our principles. 

Attachment means you can't let go of how someone treat you or self-centred concern. Adhering to principles mean doing the right thing, righting the wrong.

Adhering to one's principles is not the same as attachment. Adhering to our principles amidst temptations and difficulties is a positive force for improvement. Attachment is self-centered concern about fame and gain, which keeps us bogged in delusion.