My No.1 trading Rule

If you're not a day trader or are not playing stocks full-time then only invest with excess money that you have and never your entire fortune, especially if you are not doing your own due diligence but buying based on speculation or hearsay. Cause you'll never know when and how the stock market might crash.

By only investing with your excess money even if the market do crash at least you're not broke, and can at least hold on to the stock and wait for it to go back up. Paper loss is not a loss till you sell it.