Patience…lots of it…it’s not a quick fix or an easy road and can be really trying on both of you.
You also have to be prepared to just listen and hear them. They’re not necessarily looking for someone to provide a solution, but just someone that they can talk to and be heard by so they can just relieve some of the pressure and know that they’re not going through this on their own. Once they’ve done that, then you can start looking at how you can take each issue in turn and see what can be done to address any of them.
Sometimes you could find that it’s a traumatic event from their past that has been re-triggered by a present event, sometimes there might just be no reason for it.
Depression and anxiety I don’t think ever truly go away, you just learn and try to help your partner learn how to cope with the darker days and always try to aim for less of them – whether this is with the help of medication, therapy, combination or whatever works for the person or for both of you in some cases.
Finally, and possibly most importantly…don’t forget yourself. You are only going to be able to help your partner if you look after yourself as well. It can be very hard not to fall into depression yourself. And just remember, you might also need to talk to someone too, don’t leave it until it’s too late.