When you hear the word "investing," you probably think about stocks, bonds, maybe commodities. It's far less likely that your reflex will be inward - but indeed, you can, and should, invest in yourself, too.

Investing is an enormous industry solely dedicated to the idea of using capital to create more capital. We highly suggest you do it. But in many instances, investing time and energy - which, just like money, are in finite supply - in yourself can lead to a meaningful payoff, too. And sometimes that payoff includes the accumulation of wealth.

It's just a matter of application, and making a plan.

To that end, here's a rundown of 13 different ways to invest in your career, your mind and your happiness that have nothing to do with buying low and selling high. Becoming a more marketable worker, earning a chance to be your own boss and simply broadening your horizons can yield rewards, too.

Find a Mentor

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Spending time with a mentor is one of the best investments you can make. Mentors are plentiful. It doesn't cost much to talk with them - just the price of a cup of coffee, or maybe an Uber trip if your mentor works elsewhere. And they can provide you with a wealth of benefits: They can improve your current job skills, help you network within your field and potentially become an employer in the future.

What workplace mentorship looks like will vary from one employer to the next. But in almost all cases, it could and should involve a senior employee acting as a guide for a newer worker with less company-specific experience. In some cases where management is willing to provide time off and funding, leadership "camps" and team-building experiences can also make employees more effective.

But what if your employer doesn't facilitate such programs? Be the organizer of a formal, company-wide effort that pairs newer workers with veterans. It's not a difficult sell. Your boss will benefit