Harry Truman is famous for saying, "The only thing new under the sun is the history we haven't learned." And I submit that there are three important lessons from the financial crisis that most of us still haven't learned--or at least haven't demonstrated we've learned. And we ignore them at our own risk.

Lesson #1: Only invest in the things you truly understand.
In the financial crisis, investors were plowing money into sub-prime mortgage-backed securities without truly understanding the increased risk that sub-prime lending was introducing. It's critically important to invest only in the things you truly understand--be that technology, marketing, sales or human resources. I've witnessed way too many companies get burned because they didn't fully understand what they were investing in.

Great vendors and supplier partners take the time to ensure you "get it". If you don't understand what's being proposed or why it will work, then ask for clarification. If your partner is unwilling to be transparent with you, then maybe he or she is not the right partner with whom you can be successful. Don't assume that you'll be successful implementing something you don't understand.

Lesson #2: If something seems too good to be true, it is.
Right before the financial crisis, the returns on sub-prime mortgage-backed securities where extremely attractive. People were making a ton of money and there didn't seem to be any end in sight. Even though there were many signs that something was not right (at least in retrospect), no one wanted to stop that gravy train from speeding down the tracks. That is, until it completely derailed.

Long-term successful business growth is not about taking short cuts. Unscrupulous sales people prey on our universal desire to find a better, faster, cheaper and easier way. Logically, we know and understand when something is far too good to be true, but our temptation to take shortcuts requires diligence to keep in check. This is especially true if we don't truly understand the shortcut we are investing in (per Lesson #1 above).

Lesson #3: Contrarian views can be hugely profitable.
During the peak of the run-up of the sub-prime mortgage-backed security investments, there were a few contrarians who "saw a truth that others didn't see" (to borrow the insightful words of Peter Thiel). These investors began to bet against the long-term viability of these investments and when the crisis ensued, they had the most to gain. They profited from their knowledge, understanding and beliefs that most people got this one wrong, and they prevailed when so many others incurred terrible losses.

In your industry, you need to ask yourself the same question: Have you identified a unique opportunity that others don't see? If you've done your homework and have a good answer to this question, you can build a billion dollar business around this insight.

In any business, insights are the cornerstone of growth. Gaining new insights is important, but implementing what we have learned is even more important. Thoughts without action are missed opportunities that really won't amount to anything.

Instead, look to take action on these lessons with partners and co-conspirators who share your passion, purpose, and mission. The people who truly care about your success are the ones who will work tirelessly to ensure your long-term viability and growth. Let's learn from the financial crisis and put these important lessons to work for your business.

Published on: Dec 2, 2014
The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.