(Business 2.0) -- On a typical day, I"m surrounded by a lot of people who are probably smarter than I am, whether I"m in a classroom full of MBAs or in a boardroom with top executives. But I"m wise enough to know one thing that many of them overlook - or at least underestimate - about what it takes to succeed.

Bear with me for a moment, as this philosophical nugget will sound hopelessly banal to some, painfully obvious to others: All the brains and connections in the world won"t matter unless you also have the bullheaded determination it takes to get things done.

I was reminded of this fact during recent visits with a handful of foreign and domestic CEOs, each of whom independently mentioned the don"t-give-up mentality as the most crucial ingredient to their success.

Take the story of Lars Dalgaard, the CEO of SuccessFactors, a 300-person venture-backed company in Silicon Valley that sells human resources software. Dalgaard launched the firm in 2001 by buying the intellectual property of Austin-Hayne, a company that sold a product for automating performance reviews but had annual sales of just $480,000 after seven years. Dalgaard switched the product to a Web-based version, added new applications, and hired more engineering talent to make the offering scalable. But Dalgaard will tell you that he began to build what is now a thriving company around a product that was given up for dead.

That was just one hurdle. When SuccessFactors"s first telesales initiative failed, the company tried outsourcing. But terrible customer service forced it to try again in-house - this time with a young sales team that lacked training and product knowledge. Another disaster.

So Dalgaard invested in more training, continuous feedback, and rehearsals for sales calls. Today, on its fourth try, SuccessFactors is making telesales work: Revenue is growing at 120 percent annually, and telesales, Dalgaard says, is a significant part of the growth.

The lesson? Learn from what isn"t working - a skill Dalgaard considers rare in today"s corporate culture, which, he says, "is optimized more for an IPO than for building a sustainable company."

Sanjay Chakrabarty, the 35-year-old founder of Mobiapps, learned the hard way about giving up too soon. The Singapore-based company, Chakrabarty"s third startup, sells mobile equipment-tracking systems. His first startup（创业）, which he launched as a college junior in 1990, focused on client-server applications. But when he and his two partners got job offers after graduation and someone was willing to buy the company, albeit for a pittance, they sold.

A few years later, when he discovered a similar startup grossing tens of millions of dollars, Chakrabarty realized he"d tossed in the towel too early. Today his perseverance is paying off at Mobiapps, which recently won venture backing from Intel Capital and 3I.

Chakrabarty earned his master"s at Carnegie Mellon but says he"s learned more in the years since. Many MBAs, he says, are geared to the intellectual rigors of running a company but can be reluctant to get their hands dirty, believing that smarts and connections will open doors so they won"t need to do the actual work.

"You need the persistence," he says, "to deal with the difference between what your plans predict and what actually occurs."

That resilience is especially crucial for small businesses. As one study of 29 small firms operating in depressed regions of the United States found, some companies are great at making something out of nothing, while others aren"t.

For instance, the billing manager of a small telecom startup that wanted to offer a variety of calling plans taught himself the software and cobbled together a system that saved back-office costs and still allowed tiered pricing. The difference between success and failure among companies in the study came down to either accepting resource constraints and giving up, or seeing possibilities others didn"t.

As you think about qualities to seek in new hires--and in yourself--take seriously that other philosophical nugget, from Woody Allen: "Eighty percent of success is showing up."