It's easier for other professions, like programming, where you have unlimited chances. If your code isn't right, you can correct it. With sales, that isn't the case.
In sales you only get one try (or a second one if you were marginally convincing the first time around).
If you are working on a product that has a limited number of prospects, how do you get over the fear of potentially wasting leads? It's hard not to constantly thing that your presentation isn't perfect yet, or you need to tweak your email templates more, etc.
It sounds like you're envisioning a sales process where you push your product onto (potential) customers and they have the chance to say "yes" or "no". This method is suicide if you're in the business of selling to a limited number of prospects.
You need to open a dialogue with the (potential) client, that ends up with them buying your product from you, instead of you selling it to them.
@Nick is right about engaging with prospects prior to "selling" to them as the way to go.
Apart from that, do keep in mind that sales is a numbers game. You'll never be able to convert 100% of prospects. But you can do things to increase your odds. Instead of being, thinking, acting, breathing like someone selling something to another person, become the expert in your niche.
Create content and connect with other influencers. Become the influencer and sales will follow.