I’m not really clear on what you did or omitted that you think is a mortal sin. If you felt you were judging someone harshly, I’d say that has more to do with an attitude and levels of love and understanding towards one’s neighbor but actually mortally sinning by having judgmental thoughts towards a person.?! I think that is a stretch and it may lie in your basic understanding of what makes for a mortal sin.
I suppose if your thoughts about a person were simply “I think that person is wrong in doing what she’s doing and she should stop,” that may be judgmental about her doings, but it isn’t a mortal sin. However, if you spent weeks judging her every action, say at work, and developed a pure hatred of her because she could do nothing right in your sight and hated her from the depths of your heart, then, yeah your judgments of her may be very sinful but what is worse is the hatred that spawns the judgmental attitude in the first place.
We are warned against judgment by Jesus because it is an attitude that leads to many grave sins. But making a judgment call over someone’s behavior while watching the news isn’t exactly a mortal sin. It can lead to mortal sin if you let it tae you there. There is a saying around parts I visit and it goes like this: “No one can take you where you don’t want to go.” Meaning it is your choice to harbor hatred in your heart for anyone or anything and you can love a lot easier. Those who strive to love like Jesus seldom get caught up in the pettiness of a judgmental attitude.
Hope this helps.