Never stop learning. This was the most important advice on leadership I ever received. It wasn't until I opened my business fifteen years ago that I realized this doesn't mean just pursuing a higher education. It means that if you view every person you meet as your teacher, it is impossible to stop learning.

Running an eCommerce logistics business, I've had the great fortune to work with diverse and energetic entrepreneurs. Our company has helped businesses like Birchbox, Adore Me and Vineyard Vines grow from emerging brands to globally recognized companies. However, for every business we've seen expand, we've seen an equal number collapse. Even businesses founded on truly innovative ideas can crumble if they don't commit to learning and growing with each new partnership.

Here are the five most important leadership lessons I've learned from my clients-my best teachers:

1. Be humble.

While I'm proud of the level of innovation and service at our company, the creative selling models and the scope of exciting and new disruptive ideas produced by our talented clients never ceases to amaze me. From subscription-based apparel programs, the commercialization of cosmetic samples, to forum and community selling, we have had the pleasure of supporting and aiding in the growth of new approaches to retail.

Interestingly, it was those that did not possess humility who taught me just how important it is not to assume that you have nothing to learn from the lessons of entrepreneurs that went before. So many businesses founded on truly innovative ideas were unsuccessful because they failed to avoid basic mistakes such as managing on-hand inventories or tracking and responding to the success metrics suggested by their finance partners, suppliers, and agencies.

Your outstanding ability to innovate in areas of design or delivery may not automatically translate into general business knowledge. The good news is, it doesn't have to. Know your strengths and then work to surround yourself with a team that compliments them.

Humility also means that you need to surround yourself with people that complement your skills. I owe the success of my organization and team to this very lesson. While it's easy to think that your business would be more successful if everyone thought and worked just like you (it's okay, we've all had that thought), it's also close-minded. I make a conscious effort to hire people based on traits and experiences that while complimentary to mine, are also different, in order to gain other insights and perspectives and to better adapt to the rapidly changing conditions in our business.

2. Invest in the success of your partners.

A few years ago, one of our larger clients hired a new senior manager who walked into my office, dropped our contract on my desk, and said, "We're negotiating or we're out." A few weeks later they brought in a group of "employees" for a site visit (whom we later found out worked for one of our competitors.) As you might expect, we did not work very hard to keep that business.

Contrast this approach with another rapidly growing client who hired a senior operations manager and charged him with going out for an RFP. Due to their growth and the internal issues their organization faced because of it, he did not want to manage the distraction and chaos the RFP process and move would cause.

Instead, he approached this with a win/ win attitude. He arranged a meeting and asked us to tell him how he could become our ideal client (read humility) and asked if I would be willing to renegotiate the contract with that goal in mind.

While I had no obligation to do so, I knew if we worked collaboratively we could remove costs from the supply chain as opposed to transferring cost from client to vendor. We conceded pricing and service level changes. He committed to more stable forecasting and internal business processes. In the end, we both won. More importantly, we developed a deep sense of trust that defined our relationship for many years.

When we work with partners, we go out of our way to understand how our own performance affects their capability to execute and to achieve their margins. We want to be their best customer so that we will get the best service. This means understanding how what we do affects their ability to succeed. By doing so, we all win.

3. Work with your ideal customer in mind.

The CEO of one of our fashion brand clients turned his company around by placing focus directly on the company's ideal customer. He asked his team and partners like us to consider how each one of their decisions affected "her," the woman opening the box.

We have clarified our ideal client to be emerging businesses who are focused on delivering a specific brand experience to their customer. We know that our clients can't, and therefore we can't, expect long-term success if our team is not delivering the exact brand experience that our clients commit to their customers. With every box we pack, track, and deliver, we keep the end customer or "her" in mind.

4. Be courageous.

My teachers have never been short of courage. Disrupting markets and creating new business models is not for the faint of heart. I've paid close attention to the rewards that can come from taking of intelligent risks. Many of the leaders I work with have bet the farm on new approaches to commerce, or have openly challenged the giants in their own verticals.

Recently, one of our clients faced backlash for her decision to sell her company to one of the largest global players in the beauty space. Because of the brand's story and reputation, she knew that many of her supporters might be disappointed in the news. Instead of hiding, she took to social media and took control of the story, never backing down from the idea that her followers should be celebrating the event as a success and next chapter for the brand. She taught me the importance of standing up for decisions that I believe in and doing whatever it takes to protect our organization's legacy.

From these courageous people I have learned to recognize opportunities when they appear. Since our founding we have aggressively pursued new space as it became available, even opportunistically acquiring a photo studio to help expand our offering for our clients. I urge my management team daily to take risks as we look for opportunities to expand--even if I'm not certain what the outcome will be.

5. Invest in the success of others.

A rising tide lifts all boats. The leaders that invest in the personal success and professional development of their teams, spending time in respectful communication, tend to lead well-aligned organizations. Those that hold information close and focus on rank tend to be the most chaotic. One of the most reliable predictors of an emerging company's long-term success is the way the organization's leadership treats people that work for other organizations as well as their own. Your ideas, passion, and education will go only as far as other people can take you.

I try to apply this lesson by catching people doing things right and then explaining how that tactic supports a larger strategy. I hold small lunch meetings with all employees, sharing objectives and listening and responding to their observations. Trust people with the big picture and they will make better decisions when you are not there.

The key message in all of this is to stay open and be ready to learn something new from everyone you encounter--from the people who got it right and the people who completely blew it. When it comes to leadership, your greatest teachers can be those that you serve each day--your clients.

What have your clients taught you? Let's learn from each other by sharing in the comments below.