Question

各路高人请指点这篇英语小作文！

I'm sorry to hear that you are not feeling well.If you get tired and have a lot of headache,you shouldn't study late.You should listen to some light music and go to bed early.Don't be often stressed out.(这一句有无存在语法错误？）It's not healthy.You must usually keep in good mood.(这一句有无存在语法错误？）And what's more,it's important to eat a balanced diet.I believe,the more vegetables and fruit you eat,the healthier you will be.
If you can do these,you will be far from illness.

Answer 1

you shouldn't study late应为you shouldn't study till late
Don't be often stressed out.语法没错但句子难以理解，你试着想想别人汉语告诉你“不要老胃疼”是什么感觉…………“不要压力太大”的汉语本意是“别给自己太大压力”用Don't push yourself too hard.
You must usually keep in good mood.不用in，keep a good mood。但这句有同样问题，must usually很怪，改为try to keep a good mood较好。

the more vegetables and fruit you eat,the healthier you will be这句话逻辑有问题……真的吃的越多越健康吗？你只是想说吃多点会比较健康吧（意思是他现在吃的不够）
最后一句far改为或后加away才对

Answer 2

没错

Answer 3

你是写给谁的。我怎么觉得语气上太过有“指导”之意？ 英文的文章很少使用这么多的“You should ... You must ...” 把语言说的委婉些就更好了。