When do you get to a point in a relationship when enough is enough?
Is it after the first time you argue? The first time that they cheat? The first lies?
Personally I believe that if a relationship is not right for you then it is time to move on. If you are not happy and you are being made ill by the other person then it is definitely time to move on. Although it may be difficult in the long run is it better to stay and be happy or go and move on. Even find someone who you truly are happy with. You could even enjoy being single for a while.
Why do you stay in relationships when you are not happy?
Is it fear of being alone? Is it fear that you might one day be happy with them?
Maybe as time goes on and you work on the relationship then maybe one day you could be happy together. Think of the good qualities and list them down. Think of the bad qualities and list them down. Which one totals the most.
Maybe depression causes you not to be able to leave. Maybe you are so low that you can't bare being alone. In these cases I think the best thing you can do is go get counselling and sort out the depression before you make any decisions. Maybe it is not the relationship but you are feeling so low anyway that you may think it is the relationship. Maybe it might get better once you have sorted out the depression. The other way it could turn is once you are feeling stronger you could realise that is the relationship making you low and once you are free of the depression you may have the strength to leave and live your life happily.
The best thing to do is think seriously about it. Don't just ignore it and hope it will go away. Nine times out of ten it won't.
Do you want to live a life unhappy anymore?