I have the same struggles, got some critical feedback on an essay and that spiraled me down in some really bad feels, lasting for some days now. Not sure it will get better or if I will feel like this for some time now, I guess we can only wait and see.

Something I realised though is that no matter what, the feelings we're having are still valid. You had some arguments and got reminded about some forgotten conflicts, of course that will affect how you feel! The sadness need to be attended to as if they have a reason. Talking to people help, getting support, maybe cry a bit. I recognised the returning sadness but I still attended to it, talked to my family about how I felt, cried some, got some supporting words and I felt better. I mean I'm still sad but it helped. I don't know how to tell how long it will last for, but I think isolating oneself or thinking it's all just a part of the episode, will not make it better. When feeling like this we need even more support and care! And whatever we feel is for a reason, if so an exaggerated one. Maybe talk to your mum about this to resolve some old things? A big hug to you and hope it's only a bad mood after all