In 2003 and 2009 my account was cut in half even though I was diversified. I thought CASH was enough of a diversifier. I now know better and will eventually add TLT as an AIMed account when interest rates invert.
I am also moving away from individual stocks, or at least that is my intention as funds can not go to zero and so I feel more confident in buying as they go down.
A few individual stocks I have owned have gone bankrupt (Meditrust, American Home Mortgage ) and Double Hull Tankers, Fuel Teck, Sunpower, Chiqita are deep divers for me.
Regarding not buying more if something goes down a lot. I have done very well with STKL as it went from 6 to 15, back to 5 and is now just under 10. Also have done well with SCCO and WRI
Toofuzzy
Take the road less traveled. It will make all the difference.