The best way to understand customer motivation (aka pain aka desire aka wants, etc) is to study human behavior and human nature.

For a VERY simple model study the lowest levels of Maslow's Hierarchy of Needs.

For more detail study Evolutionary Psychology and Neuromarketing. Type those words in to the amazon.com search box and you'll find plenty to read.

Good marketing is grounded in a firm understanding of human nature. Once you have a good grasp of these concepts you can begin to apply them to your specific market. It's part science and a good bit of art. The key is to, as Steve Blank says, "get out of the building."
It will likely take time to develop this skill but the investment and effort are well worth it.

The "shortcut" is to work with a consultant or coach who has already studied and these things and mastered this skill. They will not only assist you in specifically finding YOUR customer's "pain points" but they will effectively lead by example. And you will no doubt shorten your learning curve significantly. Consider that there are 237 responses in the amazon search for "neuromarketing" - and then consider that a good coach can direct you to the highest impact 3 or so books.... How much time and money would that save you?

Let's talk if you'd like some direction and assistance. I wish you massive success!