If you find yourself in a relationship with someone showing signs of depression, you need to be there to help. Even worse is when someone is going through what's called relationship depression. Many times a relationship will end because of this difficult period in someone's life.
Depression can make people think irrationally and causes them to be unaware of the good things in their life. If you are trying to help someone who is depressed they may make you feel like everything you do to help is a wasted effort. In reality they appreciate your efforts and are glad you are there for them. They would not blame you for giving up and leaving, in fact they may try to make you do just that.
They actually don't want you to leave, they like that your are there by their side helping when you can. Learn what you can about depression so you know the signs and what the causes are. You need to watch yourself to make sure you do not fall into depression yourself, it can be contagious.
If you find yourself falling into depression along with your partner, be quick to seek out professional help. Once both of you fall into depression you may find both of you falling deeper into it unable to get out. You need to be aware of where the depression is taking you so you can step back and take care of yourself.
Depression from a past relationship can resurface in a new one and cause the new one to fail. Failing may seem like the persons only course of action, and will go with that feeling. When you see this coming on, seek professional counseling to bring a stop to it. Sometimes even the stress of dealing with someone's depression can cause a relationship to fail and again counseling can help.