Repression is one way of looking at it... I'm not entirely sure that that is it, though... An alternative might be: State dependent memory.

The idea here is that when you are in a certain state of mind (a physiological arousal level or something like that - I will explain in a bit) then you have facilitated / better memory for other times when you were in that state of mind.

So, for example, when you are happy and positive and feeling warm and fuzzy... You are better able to remember other times / things that happened when you were feeling happy and positive and feeling warm and fuzzy.

When you are just going off to sleep... In that faintly hypnotic frame of mind... You might start to remember thoughts / feelings you were having last time you were just going off to sleep... You might even start remembering dreams or something that you had forgotten when you were in a more awake place.

They say that women 'repress' or 'forget' the pain of childbirth after having a child... If they properly remembered it - they would only have just the one!

So... If you have trouble remembering just how bad things get sometimes... That is the flipside of forgetting just how good things can be at some other times. Don't get yourself into the head space that the depressed you is the 'real you' or anything like that... It is a part of you and it has worth to contribute... But it isn't the whole you, for sure, even though it might feel like it.

I hope you get the help you need.