Building sufficient financial resources to retire early may sound like a dream, but making that dream come true is not as hard as it may sound. The main thing is simply to save more money each month. No big deal, right? Well...The typical rule of thumb given by financial planners is to have a goal of saving up to 20% of total earnings. But if you want to retire when you're younger, that percentage will probably need to be more like 40% to 50% of your income. Of course, that's not so simple since a big part of your paycheck goes to day-to-day, necessary expenses. So if you want to save that much, you need to make some serious lifestyle adjustments. It requires making changes, but it's doable.This concept of intensive saving for an early retirement has spawned a movement called FIRE (Financial Independence, Retire Early). Followers of FIRE strive to save up to three-quarters of their income, and make other adjustments too: live in small homes, walk to work each day, practice strict diet plans, and more. Even if this lifestyle may sound a bit unreasonable, the ideas behind it are worth considering.The first point is to adhere to the key principles of long-term investing, including developing a diversified portfolio that includes stocks with various styles, sizes, sectors and regions.To speed up the retirement investment cycle, you can build a portfolio structured with more risk - and the potential for higher returns. It should in any case be adequately diversified to safeguard against sharper than normal market downturns that can be hard to recuperate from and that can ruin any opportunity to achieve your early retirement goal. There are various strategies to diversify a portfolio, and how you do so should be guided by your age, your risk appetite, your growth and income needs, and your long-term objectives.Once you've begun saving at a higher rate and you have an investment plan, put that money to work in your plan as quickly as you can. Don't worry about finding the "perfect time" to invest - simply put the money in and keep it in. Let compounding work to help you grow your retirement savings at an exponential rate.You may want to look at growth stocks with attributes acceptable for retirement investing like low beta, strong earnings estimates, positive sales growth, and expected future growth.The Zacks Rank regularly identifies attractive growth stocks ideal for retirement investing. Here are just a few that might be worth consideration: AbbVie (ABBV), Bristol-Myers Squibb (BMY) and Pinnacle West (PNW). These are top-ranked stocks, with at least 5% earnings and sales growth over the past five years, and boast beta equal to or lower than 1.Do You Know the Top 9 Retirement Investing Mistakes?Whether you're planning to retire early or not, don't let investing mistakes derail your plans.If you have $500,000 or more to invest and want to learn more, click the link to download our free report, 9 Retirement Mistakes that will Ruin Your Retirement.This report will help you steer clear of the most common mistakes, like trying to time the market, lack of diversification in your portfolio, and many more. Get Your FREE Guide Now Pinnacle West Capital Corporation (PNW): Free Stock Analysis Report Bristol-Myers Squibb Company (BMY): Free Stock Analysis Report AbbVie Inc. (ABBV): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research