Here are a few things that I keep in mind when I feel like practicing some race lines but am by myself with no gates, or time to set up and take down a course.
1) get your nerves up - you want to recreate a real race environment as much as possible. Go fly hard and fast around natural gates, flags and features. Move up to more destructive scenarios as you start feeling more comfortable, raising the risk and severity of damage to hardware if mistakes happen, (they will, and should, or you're not pushing yourself hard enough). GET YOUR NERVES UP! (e.g. metal fences are a good start, also good motor killers). Get in your own head, and keep pushing
2) Stay low to the ground - pretend there are gates everywhere and find your lines as low to the ground as possible. You will frustrate yourself trying to stay low with imaginary gates, even further raising your nerves.
3) Pitch vs. Throttle management - In racing, you're not looking for the smoothest flow lines and perfect imagery like you do in freestyle, but whatever gets you around the course the fastest. When you find yourself gaining altitude, do not lower your throttle but rather, practice pitching down to regain low altitude and find yourself keeping your speed and even increasing your speed. Regulate your altitude with pitch correction, rather than throttle correction, and you will quickly find yourself cutting seconds off of your lap times. (you may find yourself staring at the ground in these circumstances, good to get used to that before race day comes with a long straightaway). It is critical to know where you are and what trajectory you are taking at all times, even if your fpv camera is not pointing dead straight in front of you. Knowing how to correct from any axis at high throttle is key here.
In the end, the idea is to recreate a real race environment, which for those who don't know yet, is always more nerve-racking than flying by yourself or with your buddies. It is sometimes tough to push yourself when you are flying alone and with no course, but these key things will help you tremendously come race day with a little attention and practice.