t’s a beautiful day here in McLean, VA. After my client meeting today I walked back to my hotel while simply reveling in the weather. The sun was very warm, almost hot, which felt delicious on my skin after a day of air conditioning—but there was also an undercurrent of coolness, nearly chill, that woke me up and kept me moving. It was the ideal balance: comfortable, but not lay-down-on-the-grass comfortable; energizing, but not why-didn’t-I-wear-a-jacket energizing.

And it occurred to me that finding the same sort of balance in one’s professional life is a key to success. As I look at my own career, and reflect on the successful clients and colleagues I observe every day, it seems to me that a great job is, at its heart, one that offers both joy and challenge.

We tend assume that it’s too much to hope that we’ll find joy at work. So we don’t even go for it. And we sometimes shy away from challenge, because we’re worried we’ll fail, or it will be too stressful. But think about the things you enjoy doing most. I imagine they make you feel happy, engaged, excited—that’s the joy part. And I suspect they also provide the opportunity for you to learn or do new things, or get better at something, or demonstrate your skills. Those are all forms of challenge.

If you’re looking to find a job or a career where you can be truly successful long-term, put joy on your list of requirements and embrace the idea of challenge.

Put joy on your “required” list. Joy at work doesn’t mean that you love every person, every moment, or every task. It means that—overall—you’re happy to go to work in the morning. You look forward to it rather than dreading it. You enjoy (for the most part), your colleagues, your work, and your company. If you’re reading this and thinking None of that is true for me, I can almost guarantee that you will not be successful at your job. People who show up grudgingly to work every day and move through the job while clearly not having a good time do not get onto anybody’s short list of employees to retain, develop and promote. Think of it this way: being unhappy at work is bad for your career. So commit to finding a job, a workplace, and boss that you feel good about most days—consider it a requirement for success.

Embrace challenge. In his wonderful book Drive, Dan Pink points to research showing that one of the things people want most in their careers is the opportunity for “mastery”—for getting better at things. Mastery arises from challenge: you get better at things when you put yourself into situations where you have to stretch. If you’ve approached work with the idea of making it as easy and stress-free as possible, you might be getting in the way of both your success and your enjoyment. We’ve all known people at work whose mantra is some version of “not my job”: whose career goal seems to be to do as little as possible. Do those people seem happy? Are they getting promoted and developed? Generally, no. The folks who embrace challenge—say yes to taking on new responsibilities, take advantage of chances to improve their skills, volunteer for start-up projects—tend to build more viable careers. They’re seen as focusing on mutual benefit; on wanting to help the company while improving themselves. That’s the kind of employee that companies want to keep and groom for bigger things.

If you find a job that offers you both joy and challenge, it’s much more likely that you’ll bring your best, most hopeful and focused self to work. And that’s the foundation of your success.