Here is an investment guarantee, and it is the only one I am confident in making. At some point in your investing career, equity markets will take a huge drop, i.e., poop will happen!
How you deal with the poop will determine your-long term investing success.
In a nutshell, don't make a rookie mistake by selling your equities in a down market. Your portfolio will recover if you leave it alone for at least 10 years.
Please see Investment Piece #5, Risk and You, for a detailed explanation of the aptitude you will need to develop to become a successful investor.