Go to bed early and it will keep you active during the day

是祈使句,不用going是因为后面还有and it will..,
以Go to bed early and it will keep you active during the day为例,如果用going,就是Going to bed early will keep you active during the day.
再问： 是复合句和简单句的区别么。 是不是说，Go to bed early已经是个完整的句子了，然后and it will keep you active during the day是什么？ Going to bed early will keep you active during the day.是动名词作主语的简单句么？
再答： 恩，Go to bed early 已经是一个完整的句子了，无需用 ing，后面的 it will keep you active during the day 也是一个完整的句子，中间用and连接的，即用and连接了两个句子，it代指go to bed early.Going to bed early will keep you active during the day是动名词做主语的句子。