I’m just finishing up writing a book for executives who are thinking about becoming entrepreneurs. I was trying to come up with an anecdote about how entrepreneurs need to be flexible thinkers, about to dodge roadblocks without much time to plan. I think I came up with one.

I went to Columbia Business School. One of my good buddies in class was an electrical engineer, whom I’ll call Todd. He designed photovoltaic cells for industrial buildings. I remember vividly when we took our first Corporate Finance midterm. The test consisted of one problem in which we had to use discounted cash-flow and other analysis to create a valuation for a company.

I got to about Step 14 of a 30-step process and then forgot how to calculate the cost of equity. After a minute of trying to remember, I made a little note in the margin: “Professor, I forgot how to do this step, so I am assuming the cost of equity is 12%.” Then I moved on to step 15.

Meanwhile, I could hear Todd in the seat next to me, and it sounded like….whimpering. Sweat was beading on his forehead….in the middle of December! When the test was over I asked him what happened. He said he got stuck after about 10 minutes (of a two hour exam) and couldn’t go on. I asked him, “Why didn’t you just make something up?” He was too dazed to answer.

We had a long conversation about it afterward. We concluded that the reason I was able to keep going and he was not had to do with our core personalities, our DNA. I am a marketing guy. I make stuff up for a living. If I’m wrong, so what? He is an engineer. If he makes stuff up, buildings are gonna fall down! He has to be right.

Once we talked it through, he was able to adjust for his personality type and vowed next time to keep going even if he didn’t know the answer to a piece of a problem. He got an “A” on the final and the course. I got a “B.” But should Todd be in his own business? Maybe not. Last I heard he is happily designing the most advanced solar panels in the industry for bigger and bigger buildings, and having a great life working for someone else.