Keep your eyes on the stars and your feet on the ground.

Well this proverb its abaut the stars are inspirational in nature so that one gets a sense of things that can be or are possible. Not every star necessarily means the heavens, stars are an endless source of inspiration no matter where and when they appear.
So basically the main idea of this is that you can have many goals but if you want to reach them they have to be rasonable, for example if a puper says i want to be the president of the country, its sounds like a very hard goal to reach for a person who lives in the streets, so you have to set your goals thinking in big things and follow the steps to get it, bearing in mind that not always you reach them.