This post is part of a series where personal finance expert Dan Solin looks at money secrets that help the rich stay rich. See more.

It always seemed to me that most people who said that money can't buy happiness didn't have much money.

It would be more accurate to say that if your unhappiness has nothing to do with money, wealth won't make you happy.

The harsh reality is that most of us need a certain amount of money to pay the bills and hopefully provide for retirement with dignity.

Investors who follow the basic lessons that rich people know will be taking a positive step in the direction of responsible, intelligent investing that will help them maximize their returns.

Really rich people understand that money can't buy health. It also can't buy meaningful relationships with family or friends.

Happiness increases with age, according to a study conducted for HSBC Holdings plc (NYSE: HBC) and reported by MarketWatch. What is happiness? Why does it increase with age?

This study implicitly defined happiness as a combination of health, freedom from financial worry, and control over one's life. According to the study, a majority of people in their 60s and 70s report being healthy and in control of their lives -- and as happy as many respondents in their 40s. This is the key finding of HSBC's survey of 21,000 people in 21 countries and spanning four age groups, each decade from age 40 to age 80.

Health is surprisingly good but varies by country. Overall, just 14% of those 60 to 79 in the U.S. said they're in poor or very poor health, while 86% say they're in fair, good or very good health. Poor health is lower in some countries -- Brazil (10%) and Mexico (10%) -- and higher in others -- Asia (18%), South Africa (32%), Russia (35%) and Turkey (35%).

I just read an interesting little blog post over on That's Fit by Rigel Gregg. It provides a link to an article at eDiets by Dr. Matthew Anderson regarding the proposition that "domestication" of our wild side can lead to being unfit. While the seed article itself is interesting and leaves plenty of room for debate, for me it re-opened the door to one of my core concepts of healthy living, which is: Health and happiness reside mostly in the mind.

Let us imagine that you just hit it big in the markets. That stock you put $1,000 into has just jumped 300%. You sold out quick and realized all your profit. After fees and taxes you will be sitting on a small fortune, providing that you follow the advice of a qualified CPA.

But answer me this: If you had spent the week prior to getting your stock market windfall beating yourself up about being 30 pounds too heavy, not having a partner, never having had the opportunity to go to college, or because your hair is getting thin, what makes anything any different now that you made a lucky pick that generated some cash? If you hang your happiness on anything that is truly beyond your own control, then that happiness shall never be found, and true health shall remain beyond your grasp.

So, as you make your stock picks and research all of your investment plans, please do me one small favor. I promise it won't hurt one bit. Remind yourself that regardless of what the markets do, your own personal happiness is kept mainly within your grasp. Yes, loads of cash can make life easier, and there are many health issues that shall be visited upon each of us that are beyond our own control. But within the framework of circumstances that create your existence, the intangible concept of happiness can be had without a price tag, and it shall always provide compounded returns when properly invested.