Believe the world is abundant and you will never have to lie. That one sale isn't going to make or break you. Lying will.
You will find integrity is the reason why companies who only market via word of mouth are so successful. So follow suit.
And to reiterate, you never have to lie if you a) believe in your product and b) believe that the world is abundant. If you feel that you have to lie to get ahead, then you need to revisit these two points because either you need to find another product to sell or you need to relook at your view of the world.