Right, I've heard that's common. I've not been in your shoes, but I've had issues with mild insomnia, and found that exhausting myself physically helps me fall asleep quickly enough to avoid the issues that would otherwise keep me up. Now, that takes more physical effort than just going for a walk, but might be worth it too. A few hours before going to bed, do pushups until you can't any more, rest for a minute and repeat. Once you can't even do one, go for a run. Run until you feel like you're going to die, and then keep running for 60 seconds. If you still feel like crap, stop, and do pushups again. Repeat until you feel like you're going to collapse. Come home, shower, drink lots of water, and relax. Then, when you're ready to go to bed, your body will both be too tired to keep you up and will be full of natural endorphins which may help the withdrawal syndrome.