Hey there! It's frustrating as none of it should have been lost, but not much we can do about it now!
My personal strategy? If I was overweight THAT much, I'd be looking to trim down that position immediately.
What I would say in terms of what to sell, is it all depends on your overall outlook for the company. If you like them, sell a certain portion where you're comfortable. 30% in a single equity would cause me to lose sleep at night for sure. 10%? Not so much.
However if you don't like the company and you just bought it to ride the momentum (I did this with Canopy Growth) exiting your position as a whole is not a bad idea either.
Right now TFII, one of our old Bull List picks that we've since removed makes up 15% of my portfolio. This is because I averaged down huge during the pandemic and ended up making quite a bit. This is an uncomfortable allocation for me. However, it's not something I'm going to go out and instantly change (30% is a different story though). Instead, at the end of the year I'll sell off half the position to get me to that 7% range, which is what I like for all of my holdings.
I do ride the momentum though, I did so with both Shopify and Canopy Growth. These stocks both made up huge portions of my portfolio due to massive gains. I was much like you, sitting with a huge allocation to a single equity. What did I do? I sold when I was uncomfortable, and felt the company's share price far exceeded where it should be. I was very, very right about Canopy and not so much on Shopify.