Agreed. If there were only do overs. The only hard lesson I've learned if I can pass it on is to never buy a stock until you tell yourself a price when to sell if it drops. I broke my own rule recently and it cost.
I started watching the tape lately, which way the markets themselves are moving.
I wish I could find it again, I agree with an article I read recently. Basically a lot of money is sitting on the sidelines after the recent 2008/2009 market dump. Bernanke has said interest rates will remain at zero for years to come, the result being people's greed will kick in and the money they see sitting in the bank doing nothing will start coming back into the markets. I think that's what you were saying with the markets racing to new highs, I think they'll keep going...
Then again, I can write about why you shouldn't be in the markets here at all... :)
Is the corollary to that, "never sell a stock that isn't going down"?
Need to consider time frame before applying corollary. When does a stock stop going up? When does a stock start going down? Not that cut & dry. What time frame? Daily? Weekly? Monthly? Hourly? A stock could be going down on a daily chart, but still be in an uptrend on a weekly chart. All depends upon one's investment horizon.