Now that's the other side of the scale: toxic negativity. The key here is to reach for a balance and accepting, that you have both positive and negative thoughts, but you always should seek for the balance. Suppressing either positive or negative emotions will lead to a bad health. I'm afraid you have to wait until your wife is willing to seek help for herself, because change starts by accepting your own need of help. Maybe you could suggest her to seek therapy to deal her issues

You are right, but that doesn't mean you have to suppress your negative thoughts, because you're just bottling them up

I don't think it's the positive attitude that irritates, but lack of empathy and avoidance of the subject. If something horrible has happened to someone, they need some time to process the situation before they can recover. You can't speed up the process by demanding them to focus on positive side. They'll do that when they have passed the trauma

I've seen toxic positivity with my own eyes, when I joined MLM. The usual small talk goes like this:
Guy: " Hi, how are you doing?"
Me: " Pretty good, nothing much.."
Guy: " Hold on! That's a completely wrong attitude! What you're supposed to say is 'I feel amazing'"
Me: "okay... I feel amazing today?..."
Guy: " that's much better! You can't let negative thoughts ruin your day! Always think the positive side!"

It became ridiculous, when his upper level contact fell into depression and this guy (along with the other yes men) ranted how weak his contact was for letting negativity influence his thoughts and not trying to get back into positivity.

The last straw was when one of the guys lost a friend in a car accident. He was avoiding the topic around the others. I went for him to let him know I was sorry for his loss. Later the yes men brought that up to me that I shouldn't talk about this car accident, because it affects negatively on the peers and that's something the guy needs to tackle himself.

The irony is that the material where they learned all about the positivity attitude doesn't even encourage suppressing negative thoughts. It literally says right in the book, that sometimes there's issues in life and it's completely fine to have bad days and grieving, but also face your emotions and seek for recovery. The yes men completely ignored this part.

Obi-Wan Kenobi knows this very well

Justice is lost