Most of us feels empty when we lost someone we love or value, when we're turned down by the job that we really wanted, when our labor is unnoticed and appreciated or when all of the things we planned seem to turned out to be such disappointments. Guess thats what the poem tries to imply based on my understanding. No matter what we do, we don't hold the future and what it might bring. We put so much effort to something that isn't even recognized. It's like unrequited love and same thing in writing, you put too much effort in writing something up but then it's not even read or not even discovered. It feels like whatever you do, there's something missing or lacking and it's called emptiness.
You can't do a thing about being unnoticed or unappreciated but it can't be the reason why you'll stop right? I mean successful people has been turned down a thousand times before their work became perfect. You can never really learn if you've never experienced failure. You need to accept the fact that life is unfair to all of us and that's what makes it fair. Just enjoy what you do and maybe in an instance, you never realized that you already reached the top. You can be successful by uplifting and inspiring others too that's why 
