Source: Flickr user Eugene Zemlyanskiy.

Most investors, including the experts, have made a few bad calls throughout their careers. However, one trait that distinguishes good investors is the ability to learn from these mistakes and ensure that they aren't repeated. With that in mind, we'd rather you learn from our mistakes than see you make your own. Here are three stocks our experts sold too early and the lessons they learned.

Selena Maranjian: One stock I sold too early, long ago, was (NASDAQ:AMZN). You can imagine how much I have kicked myself for that over the years. Why did I sell my shares? Was it because I no longer believed in the company's future or in its leadership? Nope. I simply thought the shares were overvalued.

I was not alone at all in that thinking, but here's the problem: Shares of have seemed dearly priced for most of their public life. Consider that in 2007, 2010, and 2011, its P/E ratio topped 70. The stock has recently been trading for around $550 per share, and back in 2007, 2010, and 2011, it ended those years trading for about $95, $181, and $176 per share, respectively. The shares might have seemed richly valued, but for patient investors, there was much more money to be made.

It's not irrational to sell a holding that you believe is significantly overvalued, as it's probably more likely to fall than rise in the coming year or so. But if it's a company whose future you believe in, you'll probably want to buy it back once the shares fall. The problem there is that it's close to impossible to tell when a stock has peaked or has started a rebound. You can waste a lot of time and money trying to figure out when to sell and when to buy back, instead of just hanging on for the long-term ride, accepting periods of overvaluation along the way.'s stock has been volatile over the years, and has very often seemed overly pricey. But it has delivered patient believers average annual returns of 19% over the past 15 years. I'm glad I bought back into the company a few years ago.

Todd Campbell: Sometimes, we make mistakes when we sell a stock, and when that happens, we can learn just as much from critiquing those times as we can by scrutinizing our bad buys.

For instance, I got a healthy reminder of the importance of sticking with my investment thesis when I sold Facebook (NASDAQ:FB) shares in the mid-$30's and then watched from the sidelines as shares marched to $90-plus.

I bought my shares in the teens and low $20s on expectations that Facebook would successfully monetize mobile and shares rallied sharply once the company began doing just that. However, rather than stick around, I rang the register. 

Now, I can already hear you muttering, "Poor him, he made money and there's nothing wrong with that" and you're right -- there's no such thing as a bad profit. But in the never-ending quest of trying to invest better, I can't help but be disappointed by the fact that my decision to sell was based on my fear of giving back my gains to Mr. Market, rather than because my thesis failed to pan out.

Granted, when it comes to investing I've found that a healthy dose of skepticism is better than unbridled optimism, but absent a change in my thesis, or in Facebook's execution, there really wasn't a reason to sell and for that reason, it ranks as a costly mistake worth learning from.

Matt Frankel: Admittedly, there are several stocks I bought over the years that I sold a little too early, but the one that stands out to me most is Tesla Motors (NASDAQ:TSLA).

I first bought shares of Tesla in 2011 for about $26, a little over a year after the company's IPO. In early 2013, the stock started to rise rapidly on the anticipation of the Model S, and I sold at around $55, doubling my original investment and thinking I made a smart move. Well, just weeks after I sold, the Model S received several awards (including Motor Trend's Car of the Year) and the stock shot up like a rocket -- approaching $200 just a few months later.

Now, I made money on the deal so it could be worse, but this mistake taught me a valuable lesson. I believed in Tesla's product and long-term vision, but I let the thought of a quick profit turn my investment into a trade. By the time I realized my error, it was too late. I still buy the stocks of companies whose products I believe in for the long run, but only sell if something fundamental has changed with the company -- not because the share price has risen.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.