I think there are 2 aspects, one is the light level and the other is the spectrum.
Really I think both are important, but perhaps spectrum is more important, I would prefer bright red-orange light in the evening than dim blue.
The most pernicious is light that looks yellow-orange but actually includes strong blue components in its spectrum e.g. from LEDs or fluorescent tubes. So one really good thing you can do is replace light bulbs from modern energy-saving ones to oldfashioned incandescent ones.
Turn out as many lights as you can! I never switch on the light in my bathroom, hallway or kitchen from one day to the next.
I suppose the extreme solution if you can't control or change the lighting is to wear orange tinted goggles at night...