The following is a modified post from the Motley Fool Editor's blog. You can see all the posts by clicking here.

As we close out 2009, it's a good time to reflect on the lessons we've learned (or at least reinforced) this year. Here are some of mine. I hope you'll chime in with yours in the comments section.

Momentum is a cruel mistress
March was eye-opening. We try to keep perspective by studying the past, but there's nothing like actually living through something. Remember the state we were in back then -- wholesale bank nationalization was still on the table, the Dow seemed bottomless, and we were dropping GDP faster than Accenture (NYSE:ACN) dropped Tiger. Investor psyches were even worse off. All of a sudden, that crazy neighbor stockpiling bottled water, soup, and guns didn't seem all that crazy.

Then we had the type of blistering rally that made us peek at our 401(k)s again.

Sub-lesson 1: Make your portfolio allocation decisions ahead of time -- preferably in good times, not bad. For example, the worst time to flee to from stocks to bonds is after your stocks have taken a beat-down and you're scared. 

Sub-lesson 2: Remember March when you do make your allocation mix among all the choices out there: cash, bonds, stocks (small cap, large cap, dividend payers, established foreign markets, emerging markets), real estate, etc. Make sure it's an allocation your risk tolerance will allow you to stick with.

Sub-lesson 3: Just as stock returns got turbocharged in March, they could get throttled now. It's a good time to weed out stocks that have rallied without fundamentals.  

All serious value investors should make it out to the Berkshire Hathaway annual meeting once
In May, I attended the Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B) conference (i.e. the Warren Buffett and Charlie Munger love-in) with a few Fools (see some further thoughts here). It was my first time. 

Yes, you can get most of their wisdom from the meeting dispatches, the annual letter, interviews, books, etc. And yes, from what I hear, it's similar every year. But for value investors, it's the equivalent of seeing Michael Jordan in person. 

Buffett is 79, and Munger is turning 86 in a few days.

In all things finance, leverage is dangerous  
Even some folks who saved up, put 20% down, and took a 30-year fixed mortgage have seen their financial health ruined by the housing bubble. Why? Leverage.

Companies that have viable businesses went under. Why? Leverage.

A key driver of the banking mess? You guessed it ... leverage. 

Why are folks concerned about runaway inflation? The U.S. government's increased reliance on ...  leverage.

You get it. What does this mean to you, an individual?

Takeaway 1: Do whatever you can to pare down your debt (especially stuff like high-interest credit cards).

Takeaway 2: Be very careful when you make a leveraged purchase like a house ... it can make a lot of sense to own a home (I do), but renting ain't a crime!

Takeaway 3: Be very, very careful when dealing with options. They act as a non-debt form of leverage, allowing you to magnify gains in some cases and losses in others. Like renting, owning plain vanilla instruments like stocks, bonds, mutual funds, and ETF's ain't a crime!

Takeaway 4: Don't do anything financially that you don't fully understand. Learn first. Act second.

Those are some of my lessons. It's your turn ... lesson away in the comments section below!

Anand Chokkavelu owns shares of Berkshire Hathaway and Accenture.You can follow him on Twitter. The Fool has a disclosure policy.