It is important to take the time to understand what's important to each sales person on a personal level, not just their business goals. Business goals will happen along the way but understanding what's important to them first is key. Do they want to spend more time with their family? Do they want to save for retirement? When you as a manager take time to understand each individual employee’s personal goals, you can then go the extra step of translating that to, "Here's what you need to do as a sales person to achieve that goal."
For example, years ago we had a high performing sales client who was a young, single mother and frustrated that she couldn't save enough money to buy a house. Even though she was making a lot of money as a high performing sales person, she couldn't organize a budget to purchase a home. Her sales manager sat down with her and said, "What neighborhoods are you interested in? Here is what you need for a down payment. Here's what the mortgage would look like." Once they had mapped it out, they found that she could have a down payment in six months if she increased her sales by 10 to 15 percent. Because of connecting that personal goal to business performance, her sales manager was able to hold her accountable and she ended up having the down payment ready in three months.
The single most important thing you can do to retain your employees is to take the extra time and understand what's important to them. Understand their personal goals, and then map their personal goals back to their business activities. When employees see your company as the means through which they can achieve their personal goals, they're not only going to be more motivated and loyal, it also becomes easier for your managers to hold them accountable. In terms of keeping your high performing sales people, that’s the number one thing you can do for them and your company.