The art of selling

The other day I was reading a book on investments - Contrarian Investment strategies. It reminded me of the day I had tried reading "Gone with the Wind" during high school days. There were too many characters and nothing went into my head. I dropped out at around 110 pages. Now I am at the 60th page on this book and its giving me the same kind of creeps. Too many variables to comprehend. Infact the author mentions that stock markets are full of complex variables which cannot be comprehended by a human brain and this is where everybody ranging from experts to retail investors fail (trying to time the market). Little would he have realised that his book is going to be full of such variables which would be tuff to comprehend (chuckle!!). Anyways its a do or die situation for me with respect to stock markets. I have to tame the markets to get me to the super riches. Hence I stayed on with the book. But offcourse skipping most of the sentences and trying to skim out the important parts. But I am not getting what I am looking for. I want to know when to sell a stock, how many days to hold it? But this book doesnt seem to tell me anything of that sort. Everybody knows when to buy a stock. Low P/E, Low book values, high cash flows. But when do we sell? Anybody has any idea?