Yes, I often look at the shares I have lost opportunities on (such as DYL today) and then I look at those shares that I have sold and have subsequently fallen (PNO 1.4) and I think > "thank god I sold them"!
* Stop loss as soon as it doesn't feel right * Trade Plan * Don't buy Opens if poss * Take loss, look for re-entry - not necessarily in the same day and NOT above what you have sold for * Shuffle money to higher yielding areas * Trade shares you know - trading history at least * Don't be greedy