Have been following with interest this little number,and would...

Have been following with interest this little number,and would like to ask you traders a bit about trading styles that could possibly apply to mky.In theory , had i owned Mky shares , I would have dumped my holdings at a certain level [say 10%], and rebuy at a percieved bottom , or at least a trend reversal.Admittedly some will have lost big time , but if I had bought $10 000 dollars worth , I would have cut my losses before I lost $1000 [plus fees], and not 'held' for the long term, and lost $2450 by todays price action alone.I have noticed , however , many holders actually held , thru the storm, and not sold.I was wondering what was the thinking behind this style of trade.Being a relative newb , do i missunderstand trading/investing stlyes , or are punters not admitting that they are on a possible larger loss , and perhaps ignoring a possible opportunity cost.Reading traders books ect , they always say to sell if your stock slides, then re-buy at a better time..
This is a genuine question, as i have been guilty of waiting too long to sell [CDU] and selling too early [LYC] both in recent trades... cheers in advance!!