The fourth maxim is, _seize every opportunity to act upon your resolution_. The reason for this will be understood better if you keep in mind the fact, stated before, that nervous currents once started, whether from a sense-organ or from a brain-center, always tend to seek egress in movement. These outgoing nervous currents leave an imprint upon the modifiable nerve tissues as inevitably as do incoming impressions. Therefore, if you wish your resolves to be firmly fixed, you should act upon them speedily and often. "It is not in the moment of their forming, but in the moment of their producing _motor effects_, that resolves and aspirations communicate the new 'set' to the brain." "No matter how full a reservoir of _maxims_ one may possess, and no matter how good one's _sentiments_ may be, if one has not taken advantage of every concrete opportunity to _act_, one's character may remain entirely unaffected for the better." Particularly at time of emotional excitement one makes resolves that are very good, and a glow of fine feeling is present. Beware that these resolves do not evaporate in mere feeling. They should be crystallized in some form of action as soon as possible. "Let the expression be the least thing in the world--speaking genially to one's grandmother, or giving up one's seat in a ... car, if nothing more heroic offers--but let it not fail to take place." Strictly speaking you have not really completed a resolve until you have acted upon it. You may determine to go without lunch, but you have not consummated that resolve until you have permitted it to express itself by carrying you past the door of the dining-room. That is the crucial test which determines the strength of your resolve. Many repetitions will be required before a pathway is worn deep enough to be settled. Seize the very earliest opportunity to begin grooving it out, and seize every other opportunity for deepening it. After this view of the place in your life occupied by habit, you readily see its far-reaching possibilities for welfare of body and mind. Its most obvious, because most annoying, effects are on the side of its disadvantages. Bad habits secure a grip upon us that we are sometimes powerless to shake off. True, this ineradicableness need have no terrors if we have formed good habits. Indeed, as will be pointed out in the next paragraph, habit may be a great asset. Nevertheless, it may work positive harm, or at best, may lead to stagnation. The fixedness of habit tends to make us move in ruts unless we exert continuous effort to learn new things. If we permit ourselves to move in old grooves we cease to progress and become "old fogy."