night hiking is a favourite of mine, it's a great way to practise navigation in low visibility/bad weather.
problem is you get used to it and walking in the daytime seems... mundane. it's not normal walking round in broad daylight
here's a simple exercise that helps to explain what recondoc and co were talking about with peripheral vision, rods, cones and stuff:
get a watch with an analogue face that has luminescent dots for the numbers, stare at one dot when you're out in the dark, you will see that the dot you stare at disappears, but the other dots seem brighter!
so when you go out practise looking at stuff in the sides of your vision
motivational exercise: go to the supermarket/anywhere, see an attractive female/whateverturnsyouon, and observe said creature whilst keeping your eyes fixed on the shelf you are scanning, your wife, etc. this is how you need to look at stuff in the dark.
cheers, sargey.