" a phenomenon where the engine sounds like it is running rough when you head out over unlighted terrain or water. It goes away after a while.
Believe your instruments. There are a few things that can cause disturbing visual perceptions. Your instruments will tell you the truth. For example on a hazy night, a few scattered single white lights on the ground a a few of the brighter stars being visible can sort of make the sky and earth blend and it can be hard to tell where the horizon really is.
Plan the flight. Fly the plan. It is fun to see how closely the night scenery matches your expectations.
In the future I'd suggest that during your day landings keep your gaze farther down the runway and not right in next to the airplane. This helps with height judgement in night landings. At night if you focus on the patch of runway that is lit up brightly by your landing lights you can sort of get target fixation on it and the landing may not be what you'd hoped. When you are used to how the runway looks from ten feet and five feet and one foot, your night landings get a lot easier.
Night flying is instrument flying. And ditto on the redundant flashlights.
Enjoy it. Even after thousands of hours of night flight, it is still a treat.
Happiness is not seeing another trite Ste. Maarten photo all week long.