I'm actually (I think) psychologically addicted to the internet. Just look at this! It's half past 5 AM where I live and although I don't need to wake up early tomorrow, I'm not here for any particular reason. I watched all the new videos of my subscriptions on Youtube and felt kind of bored or empty. Then, I watched a live stream of games. Then, I watched older recorded videos from that stream. I check Facebook and stuff like that, get distracted by TV-Tropes for an hour or so etc.
I also often forget to eat when I'm at the PC for a long time. I still eat 2 or 3 times a day, because I have to eat, being very underweight, but I just procrastinate it and eat dinner at 3 AM or something like that. Naturally, that doesn't really help me sleep. I don't have sleeping problems at all. I can sleep extremely long, but I miss out on most of the day.
Well, if I have to wake up early the next morning, I manage to go to bed "early", "early" meaning something between 1 and 2:30 AM. That's not so funny if you have to wake up at 6:15 AM, especially because I'm nearly always kind of tired, a sign of my other addiction:
Coffee. I'm not really addicted to it and if I sleep very long, I often forget to drink some. For example, I only had one cup of coffee today and that was only for good measures. But I started drinking coffee when I was 9. That doesn't mean that I drank my first sip of coffee when I was 9 (that was when I was 5), but that I started drinking regularly. Not much, but normally one cup per day.
When I have to wake up in the morning (in other words: between 6:15 and 11:30), I can't really go outdoors without a cup of coffee. Even then, I always get tired between noon and 2 PM. Yeah, I know, that might be because I always stay up late, but even if I sleep (just) enough, it doesn't help. It's just the waking up "early" that gets me. It's quite a strange physical addiction.
Also, I have an extremely sweet tooth. If I have enough cookies, I can eat two packages of them a day. Not regularly, but it just happens sometimes. Same with chips. Once I started, I can barely stop eating before the whole package is empty. That's probably just a bad habit, seeing as it doesn't really affect me at all because I still don't gain any weight.