By Todd Campbell Stocks may be off to the worst start in 30 years, but over the past 30 years, the stock market is up over 870%. Despite the stock market’s recent sell-off, sticking to your investment plan is still the best strategy.There’s evidence that the market may bounce soon in what is known as a relief rally.It’s important to remember that even though this year has been tough, the stock market always rebounds eventually.The market has been tough this year. Really tough. Year-to-date, the S&P 500 is in correction territory, down over 12%, and the NASDAQ? Forget about it. It’s in a bear m…