Ten years ago I was 25 and just finishing graduate school. At the time I was working in mid-management for a state government agency.

But, like many young professionals today, I was unhappy. I had what I considered a relatively substantial student loan (which is dwarfed by the average student debt young professionals currently face), and a job I didn't exactly love. 

Looking back I can see how fortunate I was to have things so many people lack.

However, at the time I wanted to do big things and start changing the world, and that wasn't happening the way I hoped it would.

Ten years later, if I could go back this is what I would tell myself:

1. This too shall pass.

Bad times come and bad times go. Good times come and good times go. It's common knowledge not to let the bad times drag you too far down, but it's important to not let the good times pull you too far up, either.

Learn to value the people and relationships that consistently bring you contentment, rather than having your perception dictated by the fleeting victories and losses we all experience.

2. Play the long game.

If you're in your mid-twenties you still have at least four decades left in your career. If, like me, you are in your mid-thirties you still have at least three decades left in your career. Make sure you are playing the long game.

Envision where you want to be at the end of your career and make a (flexible) plan working backward from that end goal. 

3.    Don't wait for your company to invest in you. Invest in yourself.

One of the biggest mistakes I see people of all ages make is believing that professional development and training is solely the responsibility of your employer. You need to invest in your own development. Knowledge is portable, belongs to you, and will move with you throughout the many job and career changes you are likely to have.

Use resources like Coursera and EdX to get better, smarter, and faster - for free.

Whatever you do, don't wait for someone else to invest you.

4. Your network matters.

The people you know will open doors for you that your resume - no matter how glowing - will never be able to open. Building that type of network requires investing in the success of others before they ever invest in you. Successful networking is not collecting business cards or LinkedIn connections in order to build an email list.

Successful networking is sitting down and getting to know other people with the purpose of building a real, mutually beneficial relationship.

5.    You are owed nothing.

When I was 25 and finished grad school I thought I would finally get the career opportunity that I was looking for. I would finally do something that excited me.

Three years later, after many, many failed job interviews I got that opportunity.

A year ago, after building a large following on LinkedIn and starting my business, I thought clients would come rushing in the door, and getting clients would be easy.

Getting clients is never easy - but that's okay.

Nothing is ever easy, and you have to work for it every day. That was true for me at 25, 35, and I assume it will be true at 55.

It will be true for you, too.