It sounds like you'd be riding in an arena at night, right? I ride by myself in the arena at night during the week, for the same reasons as you. I was uncomfortable at first, but got myself used to it by starting a few rides on the weekends at dusk, so that there was some daylight when I started, but it was full dark by the time I finished. After doing that a few times, riding in the dark stopped bothering me as much.