<human>: Condense the text into a few key points

Me and my boyfriend have been together for half a year now.We knew each other from online dating and we were really connected and comfortable with each other so we started relationship after the third date. 

I know he has suffered from depression before but I haven't recognized how much it affects our relationship until recently. He is very negative toward people and outside world. He constantly judges others with negative comments. Since he quit smoking after dating, he tends to get angry pretty fast and easy. He loses control of himself when he gets annoyed. And he gets annoyed by many simple stuffs. His negative emotion influences my mood and I will get grumpy pretty fast if I notice some bad emotions from him. And then he starts to complain about my grumpiness and he uses bad words like "don't act like a B***". 

I said I had enough of that he didn't respect me enough. I expected him to stay calm for me, open-minded and be positive since I am negative myself and I am trying to be more positive everyday. He makes me depressed by his comments. He said I should have not expected too much from him. He went through lots of bad experience in the past and it made him so bitter about the world. He felt like the world hates him a lot. Since he met me, he has tried to be more grown up, strong for me but I should not expect him to change fast.

I said I am afraid someday he will push me off limit and our relationship cannot be saved anymore. We both broke out crying and he said he was afraid, he knew he needs to change something inside him but if the moment comes too late and he lost me.

To me, he is mentally unstable but he cares a lot for me and he is trying his best. Recently he gets problem as he easily forgets stuffs that annoy him  a lot. We argue almost every day and I cried a lot. Even if I want to stay strong, his brutal words in his anger broke my heart.
<bot>: My boyfriend said I should not have expected him to be strong and grown up too fast. He is trying his best. But he still hurts me with his words when he gets annoyed and angry. What should I do?