Ditto on the lights suggestion. Do whatever you have to to have a lighting set up that is easy to use and effective for your circumstances. I have a generator system I built around my front wheel hub, so I ALWAYS have a front (white) and rear (red) light. If I'm going on a really dark trail or it's snowy or foggy, I'll also use my helmet mounted battery powered incredibly bright light.
As for motivation, well, hell, why not?? It's a relaxing and fine thing to buzz along a road in the dark. As long as you can be seen and see yourself, you will be safe. I sometimes think I am more safe riding in the dark, as usually there's less traffic and I'm lit up so I must look like an alien invader --- freakishly noticeable to drivers.
I don't know if you're in a rural area for any part of your route, but a few times at night I've encountered deer by the roadside, and I don't know who was more startled, them or me. One time, I swear this huge creature was less than a foot away from me. Scared the living crap out of me. So, the noiselessness of a bike can put you at some risk there; I've learned to whistle or hum loudly when I ride in an area likely to harbor that sort of wildlife.