There are of course no guarantees on gains or preventing losses of your portfolio, but maintaining your preferred allocation can help spread the risks of your investments more in line with your risk tolerance and lower the levels of swings you might see in your account over time.
Investors who rushed to sell out of stocks, rather than rebalance to their target, long-term allocation plan, missed out on a chance to recoup a good chunk of their losses.
The common assumption that has prevailed among money managers over time is that asset allocation among stocks, bonds and cash helps to mitigate the risk of suffering market losses through diversification.