I grew up near Ottawa, and had a lot of friends whose parents worked at Nortel. They were compensated with a lot of stock, which they held onto (it keeps rising, after all). Their pension plan was mostly invested in the company stock too.
When the company fell apart (let's set aside whose fault that is- different topic), they lost their jobs, their savings, their pensions, in their 40s and early 50s mostly.
And yet the average person does exactly that.
Not to mention the horror that is the tax code in US, causing you to underpay taxes... because the company that does RSUs doesn't communicate well with your regular payroll company.
To this day I don't get why they didn't sell at least say $1million and stash it someplace. Sure let the rest ride if you want to do that but man save some. I never asked them about it after their company tanked, I imagine they don't want to think about it.
So keep some but don’t keep all!