In grade ten, I often had to stay up late at night to finish assignments or projects that were due on the next day; I had poor time-management skills. And upon reflection, I realized that it was all because of the Internet: I simply spent too much time surfing the Internet or playing online games.
Therefore, in order to prevent myself from wasting too much time on the Internet, I have recently disabled—or blocked—websites such as youtube or online game sites by using hosts file.
The effect was instantaneous. Immediately, I found that I could do close to nothing on the Internet, and as a result I would either sleep (replenish my energy) or actually work on my assignments/projects. And ever since I have done so, I have never had to sleep later than 12:00.
I hope this would be enough to solve my problem of Internet addiction...