Recently I've been reading "Meditations" to learn more about Stoicism and one of the main points in the book is to ignore people who do you wrong and only show them good will in return. In addition, a main point is that pain and suffering only lies in our opinion.

I have recently taken these beliefs to heart and am trying to apply them to my everyday life. The issue I face now is when do you draw the line and stick up for yourself? There are people that have been talking shit about me behind my back and in one instance right in front of me (although they didn't intend for me to hear). I understand that they are only talking shit to hide their own insecurities and frankly I don't care about their opinions. They are nice to me one on one and will even ask me to hang out, but then go and talk shit with their friends. They have been talking shit about me to people I do care about and this is where I am offended. So where do you draw the line and stick up for yourself? At a certain point I feel like I have to stop just ignoring them and say something.