Protect your principal
Successful professionals in occupations the world over use tools to accomplish their goals. Whether intangible, such as knowledge and discipline, or tangible, such as stethoscopes, violins, or race cars, these tools are cared for.
I'm sure Nolan isn't going to drag his stethoscope behind him as he makes hospital rounds.
As a trader, your tools consist of market knowledge, mental and emotional discipline, and your trading account. Protect your money in your trading account at all times. Don't abuse it, treat it carelessly, or allow others to take it from you. This money is your most cherished tool, and we must guard it with our lives.