Based on our most common conversations, busyness today is an epidemic--even more so than it was for previous generations with less technology available. In fact, it can be a point of pride.
The truth is that we are not too busy; we just have too many choices to make clear priorities. One of the worst things you can say to someone in business is that you "are too busy."
Unfortunately, other people may be smart enough to understand your real message, even if you don't realize it yourself:
You don't care.
It's OK, as you can't care about everything--the very nature of something being a priority is that other things are less cared about. The first step, though, is to know yourself well enough to understand that you don't really care. The next step is to find a gentle way to say no. Start here.
You are inefficient.
Perhaps the most damning view is that you simply can't handle your business time efficiently. This perception goes double for fellow entrepreneurs: Many of us launched successful startups while juggling other personal and professional commitments. We're the last people you want to tell "I'm too busy." Instead, explain that you're working hard to give excellent attention to your current projects and, if possible, you will make room for other projects in the future.
You aren't serious about your business.
How many times do successful businesspeople turn down work? Quite often, actually, but it is because of their clarity of focus, not their busy schedule. It is a novice move to burn bridges or close doors prematurely, as your busy season today may turn into a slow churn tomorrow.