Always be sure you're at your best.
There is a certain psychological effect a little bit of competition can have on your performance. To that end, a company called High Rise Garage has come up with a product called the GhostDash. It is a large heads up display which projects an image of a ghost car to allow you to see your position from previous laps, thus hopefully inspiring you to do your very best even while practicing. Any gap in lap times is also projected, of course.
The system might look a bit crude, but the software is evidently sound, and the company has a Kickstarter campaign to fund the manufacturing.