The 40/60 Rule of Investing
Huh? Well, over the course of their investing/trading life, most traders are lucky if they 1) pick the right stock and direction 2) pick the right price 3) pick the right time to get in and 4) (this is the big one) pick the right time to get out. This only happens more than 50% to the best of the best, the Soros, Livermores, Tudor Jones, Rogers, etc. of the world, and even for them its difficult. Mere mortals can hope for maybe 40% and those are ones that make money.
How you ask? Its the 40/60 Rule. You will make the right play i.e. one that has a good combination of the 4 above to show you a profit maybe 40% of the time. The other 60% of the time you will likely lose money. The key is not to worry about being right more than half of the time, the key is to make more money the times you are right and lose less the times you are wrong. This will show you a net profit. Plain and simple. If you have six trades that lose you $100 each but 4 trades that make you $200 each, you are ahead by $200. This is what professionals do with regularity and consistency and this is what most investors/traders DONT do. They assume they will be right or proven right, and fail to face the fact that there trade was probably wrong. Failing to face that means sitting through a bad decline–what traders call “draw down”. Large draw downs if avoided can make you money because by sheer coincidence you will be right on some the trades and its those trades that you manage carefully and ride out to conclusion.
Dont be right, make more money when you are. Be wrong, but get out early and lose less when you are wrong. This will keep you in the game longer and preserve your trading capital and might just make a profit for you down the road when you are right 
Interesting, I wasn’t aware of this percentage division when playing stocks. Good rule of thumb to know.