That being the case, I recommend putting only a portion of your money into a stock you’re considering. If it drops in price, you can reassess whether to move your remaining money in at the discount or steer clear until you’re truly convinced that the stock has bottomed out and is on its way back up. O’Neil would shudder at that advice, but it has been a splendid technique for Bill Miller, and for me. Good stocks drop in price frequently and speculation bids the price of crummy stocks high on a regular basis. Because it’s an unreasonable force causing such gyrations, you can’t think your way through it. You can improve your odds by investing in the best companies out there, but you can’t know what the unreasonable market will do.
―Jason Kelly - The Neatest Little Guide to Stock Market Investing