Sales is a Performance Art With No Applause

Performance arts are wonderful.  You rehearse for weeks; you have a dress rehearsal to prepare for the performance; then you perform--perhaps many times--in front of a (hopefully) approving audience that gives you a standing ovation after the final curtain.
Sales is a performance art, but the audience never applauds.  A scowl is more often the reaction of your performance.  Sales is a solo art.  The sales performance is primarily you and the customer, or customers.  The sales rep is the artist and, just as with an artist, the sales "performance" is lonely since there's no applause. It's very easy to get down on yourself, especially if the sales aren't coming and the reward doesn't equal the effort that you're putting into it.
So what do you do when you hit a dry spell?  What happens if the sales don't equal the effort that you're putting into it?  What happens when your boss starts asking you where the orders are?
Like any performing artist who doesn't get the applause they expected, the first job is to look within yourself for some of the answers. 
Are you doing everything you can do to get those sales?  
Is your product knowledge up to date? 
Is your pitch honest and clear? 
Do you really believe in your product(s)?
Do you believe in yourself and your abilities?
If you don't believe in yourself and your product, you will never convince the customer to believe.
Once you've answered those questions, honestly, you know where you need to focus. 
All sales start with a belief in yourself and your product.  (In a recent interview, even Liza Minnelli confessed that had to learn to believe in herself and the song before she could sing it successfully.)
All sales start with an intimate knowledge of your products. 
If you're deficient in either of these--believing in yourself and your product--fix it. 
When you're confident in yourself and excited about your products, you're unbeatable.