Watching TV, getting hooked on junk food, and even chain smoking don't necessarily have such devastating consequences as gambling so often has. You ask me for an example which will help us relax and that will not be (as) addictive at the same time. I can instantly name one, simple and easily available to everyone. It is reading. Yes, it can be addictive too, but this addiction is nothing compared to the ones mentioned before. And it can be quite useful on its own, apart from being totally entertaining. Even reading the forum will do (just in case, you can stick to reading only my posts as there's a lot of them)
I agree, reading is a good way to relax from hard work, and even if you are getting addicted to it, it's only better for you, because no matter what you are reading, you are, at least, improving your skills in English (or in whatever language you are using). But but that's a good relaxation after manual labor. If all you do during your work day is reading and writing, when working in a support role, for example, you can hardly relax with reading, right? So, what kind of relaxation would you suggest for that kind of people?
Maybe some kind of physical activity?
In fact, this is a fallback option to deal with any kind of mental stress, as well as the answer to the boredom caused by desk jobs. But I wouldn't discard reading altogether. It is an all-encompassing thing, and you just need to find what actually interests you, deep down inside, and then read into it to the hilt. In this fashion, you won't be so much relaxed as motivated (more of a roller coaster type of experience) because you will get something else from this activity other than just instant gratification and entertainment (read, it will be more rewarding in the long run). That's what hobbies are for unless your job is that hobby, but then you wouldn't ask obviously (this is an ideal situation but rarely the case in real life, though)