When it comes to career advice, we often turn to professors and scientists. Or, just as often, we ask business icons for the secrets of their success. These are fine sources of insight, of course, but there's one other repository of career wisdom we too often overlook- senior citizens.

With their working lives behind them, retirees are in an ideal position to report on what worked for them, and what didn't. More than mid-career strivers, they can take a long view on career happiness to see what really leads to lasting satisfaction and examine various strategies over the course of decades to see which withstand the test of time.

Which is why Cornell professor Karl Pillemer spoke to more than 1,500 elders about their professional lives, soliciting their best tips for those at the beginning of their journey. Pillmer recently outlined three key takeaways for Psychology Today.

1. Choose an intrinsically rewarding career.

When it comes to choosing a career, many of the elders had little to say about salary and status. Instead, they advised young people to focus more on the intrinsic rewards of any particular path, if they're aiming for lifelong happiness.

"They say it's vastly preferable to take home a smaller paycheck and enjoy what you do than to slog through a job you dislike and live for the weekends," reports Pillemer.

2. Say yes.

You don't have to have decades of experience to understand this simple principle (one 20-something CEO shared essentially the same piece of advice here on Inc.com), but it was definitely something the elders Pillemer spoke to stressed.

"At work you should embrace new challenges at every turn, and say yes as often as possible. Among of the most frequently reported regrets about work are those times when opportunity knocked and someone didn't open the door," he writes, summing up their comments.

3. Focus on EQ.

"If you want to feel good about your life when you're elderly, you need to hone your social skills now," insists Pillemer. "The elders I spoke with came from hundreds of different occupations and employers. They've seen people succeed at work and other people crash and burn. Why those very different outcomes? They told me this: No matter how talented someone is, no matter how brilliant--you must have interpersonal skills to succeed."

Still looking for more advice on how to set yourself on the road to lifelong personal fulfillment? Check out Pillemer's post for insightful quotes from some of the seniors he spoke with. Or learn about common regrets of of 20-somethings or actions you should take before you turn 30 to set yourself up for later success here on Inc.com

Anyone out there in the the twilight years of their career want to share advice for those just getting started?