I can sell and have the money in my account in 2-4 days. It would off cause be a bit sad to sell at a loss right after a "crash" or correction of the market. But in an emergency, I could.
I also keep 2 years worth of spending in the bank (we spend very little, so it is not as extreme as it sounds).
It should not really be needed, as I would get money from the government (enough to live on) if lost my job, and we have universal health-care where I live. But it gives me peace of mind.