All this will sound very trite to students of any mettle, but there are large numbers who waste no end of time working in a purely mechanical, lifeless way, and with their minds anywhere but concentrated upon the work before them.  And if the mind is not working, the work of the hand will be of no account.  My own experience is that one has constantly to be making fresh effort during the procedure of the work.  The mind is apt to tire and needs rousing continually, otherwise the work will lack the impulse that shall make it vital.  Particularly is this so in the final stages of a drawing or painting, when, in adding details and small refinements, it is doubly necessary for the mind to be on fire with the initial impulse, or the main qualities will be obscured and the result enfeebled by these smaller matters.

Do not rub out, if you can possibly help it, in drawings that aim at artistic expression.  In academic work, where artistic feeling is less important than the discipline of your faculties, you may, of course, do so, but even here as little as possible.  In beautiful drawing of any facility it has a weakening effect, somewhat similar to that produced by a person stopping in the middle of a witty or brilliant remark to correct a word.  If a wrong line is made, it is left in by the side of the right one in the drawing of many of the masters.  But the great aim of the draughtsman should be to train himself to draw cleanly and fearlessly, hand and eye going together.  But this state of things cannot be expected for some time.

Let painstaking accuracy be your aim for a long time.  When your eye and hand have acquired the power of seeing and expressing on paper with some degree of accuracy what you see, you will find facility and quickness of execution will come of their own accord.  In drawing of any expressive power this quickness and facility of execution are absolutely essential.  The waves of emotion, under the influence of which the eye really sees in any artistic sense, do not last long enough to allow of a slow, painstaking manner of execution.  There must be no hitch in the machinery of expression when the consciousness is alive to the realisation of something fine.  Fluency of hand and accuracy of eye are the things your academic studies should have taught you, and these powers will be needed if you are to catch the expression of any of the finer things in form that constitute good drawing.

Try and express yourself in as simple, not as complicated a manner as possible.  Let every touch mean something, and if you don’t see what to do next, don’t fill in the time by meaningless shading and scribbling until you do.  Wait awhile, rest your eye by looking away, and then see if you cannot find something right that needs doing.