As a society, we're obsessed with achievement. But what happens once you're considered objectively successful, with a great salary and a job that energizes you? It's easy to rest on your accomplishments and your way of getting work done, perhaps even feeling there's not much left to learn.

But in this economy, you can't afford to sit back -- even though it might be tempting.

"Successful people fall into the trap of thinking they don't need to change anything because their behavior is working for them," says Marshall Goldsmith, author of "What Got You Here Won't Get You There: How Successful People Become Even More Successful." "Every time they get promoted...they get positive reinforcement even when certain skills are lacking."

But examining where you might have shortcomings can make or break a career.

David Hale of Columbia, S.C., quickly rose to the top of the military police force and was granted the highly sought-after position of polygraph examiner with the Army Criminal Investigation Command.

"I was my own biggest fan, and being cocky, I would try to force confessions from suspects either prior to or based on their exams," he says. But he didn't take the time to understand that criminals are more likely to confess to people they like and trust. "My results fell way below other examiners," Mr. Hale says.

Mr. Hale didn't realize he needed to change until his boss transferred him and said that if his confession rate didn't increase, he would be fired. He studied forensic interviewing; worked on relating to subjects on an emotional level; and pursued courses in leadership, counseling and psychology. Eventually, Mr. Hale began to rise again in his career, and he became known as one of the top polygraph examiners anywhere.

Becoming as successful as you can be -- after you've already climbed part of the ladder -- means you need two things.

For starters, you need outstanding people skills: Listen carefully, think before you speak, reciprocate favors and manage conflicts diplomatically.

Second, you must regularly take a hard look at yourself and address your weak points. For example, if you have a communication issue with one person or a group of people, step away from the blame game and ask yourself, "How can I be better?" Make sure people are honest with you by requesting feedback anonymously and confidentially.

If you're employed by a large organization, consider contacting human resources to see what training is available. You may have the opportunity to take leadership-development courses online or in-person for free.

But the most important thing to keep in mind is that just because you're skilled or talented in a particular area doesn't mean you should simply pass go and collect your $200.

I, for instance, was hesitant to work with a speaking coach because my audience evaluations didn't mandate it, but once I learned that the top speakers in the world -- from Tony Robbins to President Barack Obama -- have worked with coaches, I changed my mind.

Says Mr. Goldsmith: "Strong leaders don't coast."