参考词汇：沉溺于be/become addicted to 网瘾：Internet addiction
I am glad to hear from you. As your close friend, I’d like to talk about the harm of Internet addiction to you as I feel worried to know that you have wasted lots of valuable time playing the Internet games.
As we know, the Internet is a convenient tool to improve our knowledge and skills. However, our life will be greatly affected if we are addicted to it. For example your grades may go down and your health will be going from bad to worse. To make things worse, it can also damage the relationship with your family. So I think it is high time that you got rid of the bad habit. It is a good idea for you to read some meaningful books and do some physical exercise.
I am looking forward to hearing your good news soon.