范文：
Dear friend,
亲爱的朋友，
Nowadays, with the development of technology, many young people stay indoors and play computer all the time. Especially for those who stay up very late or go out to play for fun until midnight, then they wake up at noon the next day. This is the unhealthy lifestyle, and they need to make some changes.
如今，随着科技的发展，很多年轻人都喜欢呆在室内玩电脑。尤其是那些熬夜到很晚或者出去玩到午夜才回来，然后第二天中午才睡醒。这是不健康的生活方式，他们需要改变。
First, having regular break time and enough sleep is the basic way to keep healthy. Some young people hang out for fun after work.
首先，有规律的休息和充足的睡眠是保持健康的基本方法。一些年轻人下班后出去找乐子。
They need to release their pressure and have fun with their friends. They go home very late and then next day get up, preparing to work. In the long run, they not only have low efficiency, but also damage their bodies.
需要释放压力，和朋友们玩得开心。之后回家很晚，第二天又早早起床，准备工作。从长期来看，他们不仅会导致效率低，还伤害了自己的身体。
Second, keep the balanced diet. Most people are picky about food. They only choose the food they like and lose the balance of nutrition. For most kids, they like to have meat and refuse of the vegetables and fruit. It is not good for the growth of their bodies.
第二，保持均衡饮食。大多数人都对食物挑剔，他们只吃喜欢的东西，营养不均衡。对于大多数孩子来说，他们喜欢吃肉类和蔬菜，不喜欢吃水果。这是不利于他们长身体。
The healthy lifestyle helps you live the harmonious life. Besides having enough sleep and keeping balance diet, taking exercise is also in need.
健康的生活方式能让你生活和谐。除了拥有足够的睡眠和保持均衡饮食，锻炼也是很有必要的。
Thank you for your letter dated March 15th and I'm glad that you are doing pretty well in everyting except that you are too busy and you'd like me to say something about healthy life.
Well, I think healthy and happy life starts with eating which should be healthy and happy too. First of all, try to get more pleasure from eating. Stay away from junk food. Try the simple, easy, nice and healthy food. If possible, try some different styles of food. Love what you eat and make it simple, tasty and healthy.
I'm sure you know that enough sleep is important. So make strict schedules to guarantee your sleep time. Lack of sleep may result in serious health problems. So just relax and plan well and go to bed on time.
Last but not the least, take sports into your life. Choose a sport or anything you like and stick to it. It's better to find some friends of the same interest so that you can go together and share your experiences. I now play badminton twice a week with my friends. It is great fun. We play in a big badminton court. You make new friends there too while you play sports.
To conclude, we all need to eat, sleep and play well to lead a healthy life. And I think we also need to learn to live a simple, easy and slow life.
Hope what I've said can be some help to you and look forward to hearing from you soon.
David
希望对你有帮助，记得及时采纳哦。