Personal growth is a worthwhile goal, no matter how you choose to define it. Learning new skills gives you greater value as a professional and more opportunities for your career, hearing about others' experiences can help you avoid mistakes and make more prudent choices, and getting feedback on your actions can help you set better goals and streamline your work.

But of course, it isn't easy to force growth in yourself. Mustering the motivation is a feat in itself, but beyond that you have to know what you don't know--and not many people do. Instead, the best way to spark personal growth is to surround yourself with people who will challenge you to do so.

Take, for example, these seven types of people who can stimulate growth in your life:

1. Harsh Bosses. There are lots of different management styles, some of which are easier to handle than others. Most of us believe we'd like a boss who goes easy on us, forgiving our mistakes, gently reassuring us when we don't meet a goal, or giving us tons of praise when we do something right. But it's the opposite type of boss, who seems to criticize everything, demand perfection, and limit praise to truly exceptional achievements, who can inspire more personal growth. Harsh bosses give you important feedback on your performance, and try to force you to be your very best (as long as they aren't destructive or spiteful in addition to their harshness).

2. Argumentative Coworkers. When you're in the middle of a team project, on the surface it seems easier if everyone just picks a leader and goes along with whatever he/she sets out. That way, no one gets in the way and no one slows the group down. But an argumentative coworker, who speaks up in favor of an alternative view, can help you realize the flaws you may not have otherwise noticed in your core idea. And argumentative coworkers in other situations, such as company-wide meetings or even hallway conversations, can similarly challenge your preconceived notions and lead you to new revelations about your work.

3. Honest Friends. Friends come in all shapes and sizes, but many of us are tempted to surround ourselves with friends who flatter us and tell us what we want to hear. A truer type of friend, and a more important one for personal growth, is an honest, direct friend. An honest friend will tell you when you're being a jerk, or when he thinks you should quit your job, or when he notices you've given up on a dream you had a long time ago. You may not want to hear these things, but your honest friends will tell you regardless, giving you an opportunity for introspection and growth.

4. Competitive Rivals. Capitalism is built on a system of rivalry, and without getting into the merits and drawbacks of the system, it's theoretically designed to inspire bigger, better things from entrepreneurs. Rivals, whether they exist as competing entrepreneurs or aggressive coworkers, can similarly inspire the best in you. You're given a challenging moving target to hit, and oftentimes you'll need to improve your own abilities to hit it. For example, you might take new classes, put in extra hours, or perfect a new skill in order to out-compete your rival for an upcoming promotion. Those self-improvement opportunities stick with you for the long haul.

5. Inspiring Mentors. Mentors can come from anywhere--they might be family friends or fellow entrepreneurs. They could even be strangers you met at a professional networking event. The point is, you look up to them as a role model, and they've achieved some level of success that you, too, hope to achieve. Mentors will directly challenge you to grow more than all the other entries on this list because it's one of their core duties. Mentors exist to give their mentees direction and insight for independent growth, in whatever form that takes.

6. Insightful Employees. Whether you're the leader of an organization or the manager of a small team, insightful and independent-thinking employees are another gateway to personal growth. You can't possibly think up all the ideas in the world by yourself, but the tangential lines of thought coming from your employees can serve as complementary considerations. The thoughts, insights, and ideas that come from your staff can illuminate possibilities you never even considered--so encourage your team to think openly and bring their best ideas to the table.

7. Random Strangers. Finally, never underestimate the power of a simple conversation with an as-of-yet stranger. The entire purpose of networking events is to connect professionals with other random professionals in the area to exchange thoughts, ideas, and experiences--but networking events aren't the only places you can meet people. Try striking up a conversation with people on the street, or the bus, or anywhere. You'll be amazed what perspectives and ideas you'll learn in doing so.

These people aren't always easy to deal with, and they aren't always pleasant to be around, but as long as they aren't malicious in their attempts, they'll serve as the challenge you need to improve yourself. No one ever became better at anything by taking the easy route forward. Accordingly, you'll need to hit some roadblocks before you find yourself capable of true inner growth.