will my partner and i survive his depression?

My partners has just been diagnosed with depression, he had it last year as well, but that was before we got together. I feel useless cos there is nothing i can do apart from be there for him when he needs me. Yesterday was a very low day for us, he didn't speak to me for nearly 7 hours. We had had a disagreement over nthing really, i slammed a door and he thought i was being funny but i was not as i did not mean to slam the door as hard as i did. I spent most of the day crying and he knew i was and still did not say anything to me. He aploygised for it this morning, i told him it was not his fault, it is just the way he feels. I am worried that we will not survive as i a couple. He is my soulmate and i can see us together in the future. He says he cannot see into the future yet, he is just taking it one day at a time, which is right way to look at it, i know. I intend to be there for him through it all, i just wonder if couples do survive depression or do they fall apart.