I think what gets you through a small writing project, is just one burst of inspiration. A book, especially a longer book, it's a different kind of force that pushes you through it. It's a vision of the whole thing.
In ancient times music was the foundation of all the sciences. Education was begun with music with the persuasion that nothing could be expected of a man who was ignorant of music.
Youth is the period in which a man can be hopeless. The end of every episode is the end of the world. But the power of hoping through everything, the knowledge that the soul survives its adventures, that great inspiration comes to the middle-aged.
The mind in creation is as a fading coal, which some invisible influence, like an inconstant wind, awakens to transitory brightness; this power arises from within...could this influence be durable in its original purity and force, it is impossible to predict the greatness of the result; but when composition begins, inspiration is already on the decline; and the most glorious poetry that has been communicated to the world is probably a feeble shadow of the original conceptions of the poet.
To engage in any activity, the warrior needs to know what to expect, how to achieve the objective and whether or not he is capable of carrying out the proposed task.