I'd try shadowing your clients. Have discussions/sessions with them on occasion where you investigate their goals, what benefits your service brings to them, and any frustrations that they have generally in hitting their goals.
"The Customer-Driven Playbook: Converting Customer Feedback Into Successful Products" by Travis Lowdermilk and Jessica Rich might be a good option for what you're trying to accomplish
"The Customer-Driven Playbook: Converting Customer Feedback Into Successful Products" by Travis Lowdermilk and Jessica Rich might be a good option for what you're trying to accomplish