I think the interesting question would be how often do you have a biggest day ever, and how much larger is it than your previous? Doubling up an account once in 1987 is a heck of a lot less impressive than consistently setting new records for biggest day ever.
My best day of trading was in August of 2007. My trading account was down $85,000 after an issues with my automated trading system-I was an option market maker, making markets in 12 options, one was RIMM. When my PC froze, the stock dropped 4 points and I bought 65,000 deltas with DITM calls and some puts when the stock was around 235ish. Basically, my markets went 5 points wide but all my markets did not move. 100D calls and puts were not moving with the stock.
I ended the day with a profit of $15,000 and my EOD postions looked like reversals on many strikes. (I had to hedge all the calls I bought and puts I sold with selling stock). It took about an hour for the stock to retrace the drop. When the interest and margin cost were all charged over 3 months, I broke even on this $17mm position. That was very scary vs the size of my account.
Sometimes our best days are avoiding bad situations. I have a few other days like this where I started the day with a large loss but recovered by staying in the game and not panicking.