I had a dream where my eyes where taken over by darkness

I always heard it's a bad omen to see yourself in the mirror in your dream, but this is something I heard years ago so I don't remember the reasoning.
I had a dream that I saw myself in the mirror, the room/setting looked infinite and the mirror was plain and simple squared.
the reflection was foggy and running out of colour but I could see darkness taking over my eyes... like black spidery foggy clusters contaminating them (I was unsure of whether they were coming from within or entering me.
However I had no idea this was my own reflection initially, so I was mentally freaking out about what was going to happen next but carried on calmly analysing on the outside. I looked closer into the mirror to see the eyes and saw pitch black darkeness (no iris, pupil or white part) this was the moment I realised it was me and I calmed down moved back and the mirror faded away.
What does this mean? Why would I feel better knowing it was me? Would that not make it all the more worrying?