There’s a saying in business that we’ve all heard before concerning a time-tested axiom that’s been true for decades:
At some point in just about everybody’s career, the difference between coasting through your professional life and actually becoming successful is no longer about one’s actual level of technical skill. From designers and developers to managers and salespeople, your actual talents, be they painfully cultivated or God-given, are only going to get you so far. No one succeeds on alone, and you often need to have the right connections to get your foot in the door for some of life’s most promising opportunities.
The difference that many eager professionals make is failing to know the difference between getting their foot in the door and inserting it into their mouth. I’ve lost track of how many times someone has pointed somebody my way for a particular service I needed only to see him get in over his head by taking on way more than he was equipped to handle. And thinking back to when I was first getting started, I can think of plenty of times I did exactly the same thing myself.
For example, there was a period when I desperately needed a talented but affordable graphic designer to put together some creatives that nobody in my circle seemed to be able to handle. A friend finally turned a young man fresh out of college my way who was just what I was looking for. He had experience in all the right programs, an excellent eye for design and just needed an opportunity to pad out his portfolio a bit. Finally, I thought my search was over.
The trouble started when he claimed that he was equally equipped to handle a variety of web development projects that we really already had good people for: some light coding and basic WordPress stuff, mostly. He seemed enthusiastic, so I let him at it. Not only did he get in over his head, which happens to the best of us, he was unwilling to come out and say as much. After the delays started piling up, it was time to let one of our regulars wrap it up while he finished the designs he was originally brought on for.
As far the graphic design work went, 
his finished product was superb. The problem was everything else, and his inability to recognize what he didn’t know. In the end, I thanked him for his work, but none of us were inclined to call him up the next time we needed similar material. This was a shame, because he was clearly a talented designer, and we could have given him a ton of work if he had stuck to what he knew.
In my experience, these kinds of experiences are more like the rule than the exception when it comes to working with newer freelancers. Looking back, I shudder to think how many times I probably behaved very similarly with some of my first clients.
Being able to admit to yourself and others just how much you don’t know is a behavior that clients who have been burnt in the past find extremely refreshing. By cultivating the humility to be upfront about exactly which skills and services lie within the areas of your expertise will help build trust in your professional relationships and allow you to focus on that which you are most passionate about.
After all, at the end of the day, building a reputation based on credibility and reliability is worth far more than a few extra billable hours early on.