Here is a word of advice for girls written by Frances Willard, considered the most influential woman of the 19th century and was commemorated on a U.S. postage stamp.  I think her advice is  equally good for boys. 

“My dear girls, dreaming is the poorest of all grindstones on which to sharpen one’s wits. To my mind, the rust of woman’s intellect 

and the worm in the bud of her noblest possibilities 

has been this aimless reverie: 

this wandering of thought, this vagueness that ends in emptiness. 

Let us look inward, those of us who are not fully engaged in work of brain or hand. 

What do we find? 

A mild chaos; 

a glimmering nebula of fancies; 

an insipid brain-soup 

where a few lumps of thought drift in a watery gravy of dreams. 

And since nothing comes from nothing, what wonder if no brilliance of achievement seems likely to light our future? 

Few women, under the present order of things, can claim complete freedom from this grave intellectual infirmity. 

Somehow one falls so readily into a sort of mental indolence; 

one's thoughts flow onward in a pleasant, gurgling stream, 

a sort of intellectual lullaby, 

coming no-whence, going no-whither. 

Only one thing can help you if you are in this extremity, 

and that is what your brothers have — 

the snag of a fixed purpose in this stream of thought. 

Around it will soon cluster the dormant ideas, hopes, 

and possibilities that have thus far floated at random.” Frances Willard.