Last year, my mom got diagnosed with breast cancer. I was in New Zealand on the other side of the world when I found out.
Flew back to the UK. But it's what started many many months of depression, anxiety, and other mental health problems.
Like the adage goes, "this too shall pass." Although it might not seem like it, eventually, things will improve. Like you said in the outro, you'll come out of this much stronger, and will know how to deal with such emotions in the future.
I'm sorry you're going through this. Sending you a massive hug. And obviously, feel free to send a DM if you ever need to talk.