When To Give Up

We all have that job, friendship, relationship that is a struggle.  We give it everything we have, pour our soul in to it to make it work. Heartaches, miscommunications, doubt, trust, respect, are ebb and flow.  Nothing is 100% perfect at all times.  The best we can hope for is 50/50 most of the time.  But when do you know when to throw in the towel and walk away?  

Is it the tears?  The constant battle of trust/mistrust, valued versus disrespected?

At what point do you accept that the friendship/relationship/job is flawed....recognize it for what it is ...and just deal with it.  I mean, once you know what (who) you're dealing with, you can handle everything....right?

In theory....yes...but we all hit a breaking point.  We try and deal with a boss or supervisor that just.does.not.get it!  They're bi-polar, inconsistent, narcissistic and would rather berate you than to give acknowledgement. 

 Or the longtime friend that is constantly sucking the life from you ...constantly telling you their woes...and gives you nothing in return when you're in a time of need.

Perhaps its a spouse or significant other that doesn't participate in the relationship (monetary, domestic or emotional)

At what point...do you say...Enough?