Diversification can help reduce portfolio risk. That's been recognized for centuries, as evidenced by the old adage, "Don't put all your eggs in one basket."
You can diversify your portfolio by putting your money in both income and growth investments,
see Asset Allocation. You can also diversify the types of stocks you own. Buying stocks from different risk levels is one way to accomplish this goal. Buying stocks from different industries, countries and market capitalizations also enhances diversification, and that can help manage risk.
A Financial Advisor can show you portfolio diversification models designed to suit investors with different risk profiles, financial objectives, and investment time horizons.