When you're done

I had a conversation with a friend a few nights ago, it was interesting.  Primarily, it was interesting, because it provoked me to think from someone else's perspective.  After I had seen it from her perspective I was able to relate it to my own perspective to better understand the situation.  The topic at hand was being "done" with people and relationships etc.  This is something that is pretty against my nature.  I feel that I can work thru almost anything with someone if they give me the opportunity and even if we differ in opinions enough we can't get along we can agree to disagree and not absolutely ignore or cut each other off.  Well, my friend was telling me about a situation in her life in which she just said "I'm done" and cut off the relationship.  I struggled to come to terms with this because I am not good at saying "we are done".  I want to fix things, talk thru things etc.  Which I guess is part of one of my problems I have previously addressed on this blog.  Then it dawned on me though, I did know what she was talking about.  I remember when my best friend of 20 years, the one who was the best man in my wedding, I remember when him and my wife cheated behind me back and I had to tell him I was done, I won't have friends I can't trust.  I wish I could tell my wife I'd not have a spouse I couldn't trust but she is the mother of my children and to maintain a stable environment for them I just deal with it.  So, my best friend and I are done still to this day.  I've not talked to him since the night I found out and told him to never speak to me again.  He hasn't years later and I'm fine with that.    I try to understand this and infer it to relationships and hurt that is not as drastic.  I try to understand being "done".  Being "done" is definitely safer and easier.  Is it really always the best though? I think that the answer varies from person to person.  We have our own bullshit tolerance levels that we can stand before we have to shut out the pain and hurt.  My levels are just stubbornly high, but that's not always healthy.  I need to learn to be done sooner and save myself the headache.  So how about you?  Are you done?  When you're done can things change back to un-done?