Such a great book; I'd like to re-read it, and I just read it ~6 months ago.
I'd say many of us around these parts of the internet are stoics. As I was reading the book, I would routinely imagine life without a few things while walking the dog, and it really does have a great impact on your happiness. I truly appreciated what I have when I performed that exercise. Lately, I haven't been consciously doing that quite as much, but I do feel like I appreciate what I have and don't mind myself always wanting more.
I believe the thing that stuck with me the most was to clump things into what you have control over, and what you don't. It's a logical thing to do, but for some reason that book really hit it home. I noticed my general stress levels drop quite a bit once I made a conscious effort to ignore things outside of my control.
One funny thing I gathered was his "extreme" example of riding the bus "like a poor person" for a week to appreciate your car. I ride the bus to work daily, and that line cracked me up.