Not only is this principle of excessive irritability to be seen at work in our more turbulent passions and pursuits, but even in the formal study of arts and sciences, the same thing takes place, and undermines the repose and happiness of life. The eagerness of pursuit overcomes the satisfaction to result from the accomplishment. The mind is overstrained to attain its purpose; and when it is attained, the ease and alacrity necessary to enjoy it are gone. The irritation of action does not cease and go down with the occasion for it; but we are first uneasy to get to the end of our work, and then uneasy for want of something to do. The ferment of the brain does not of itself subside into pleasure and soft repose. Hence the disposition to strong _stimuli_ observable in persons of much intellectual exertion to allay and carry off the over-excitement. The _improvisatori_ poets (it is recorded by Spence in his Anecdotes of Pope) cannot sleep after an evening’s continued display of their singular and difficult art. The rhymes keep running in their head in spite of themselves, and will not let them rest. Mechanics and labouring people never know what to do with themselves on a Sunday, though they return to their work with greater spirit for the relief, and look forward to it with pleasure all the week. Sir Joshua Reynolds was never comfortable out of his painting-room, and died of chagrin and regret, because he could not paint on to the last moment of his life. He used to say that he could go on retouching a picture for ever, as long as it stood on his easel; but as soon as it was once fairly out of the house, he never wished to see it again. An ingenious artist of our own time has been heard to declare, that if ever the Devil got him into his clutches, he would set him to copy his own pictures. Thus the secure self-complacent retrospect to what is done is nothing, while the anxious, uneasy looking forward to what is to come is every thing. We are afraid to dwell upon the past, lest it should retard our future progress; the indulgence of ease is fatal to excellence; and to succeed in life, we lose the ends of being! ESSAY IV ON GENIUS AND COMMON SENSE