Do not plunge or become overextended. This is worn-out advice, I know, but margin and capital worries warp your judgment and hamper your trading skill. When you think you have become familiar with technical action and can interpret market movements– and can take losses quickly!– not until then should you speculate with larger lines of stocks. There is no disgrace in being a small trader, and the market will remain open for business for a good many years to come.
– Humphrey Neill, Tape Reading and Market Tactics