From The Celebration of Mass by Canon JB O'Connell, part 2, chapter 2.
That the actions of Mass may be performed with the greatest reverence, propriety, and dignity, the rubrics regulate in detail the posture, movements, and gestures of the Celebrant. The general principle underlying these minute directions seems to be, not merely that the priest should act efficiently, decorously, and reverently, but also that when he stands at the altar as the representative of Christ he should lay aside, as far as possible, all individual peculiarities, and even the smallest idiosyncrasy, exaggeration, or affectation which might attract attention to himself, and withdraw it from the great Act in which he is engaged. Hence the rubrics concerning the position of the Celebrant's hands, the movements of his eyes, and the various liturgical gestures, aim at eliminating not only what savours of irreverence, indifference, or carelessness, but also all mannerisms or extravagances even of an apparently "pious" character. The rubrics keep the priest's movement, his looks, and his voice, within due bounds - they are laws of restraint. They are rules which aid the priest's personal sanctification, as they constitute a very real spiritual discipline. It is no small act of self-training and self-control, day after day, for example, to genuflect quite erect, or to hold one's outstretched hands parallel to one another and not extended beyond the width of the shoulders, as the rubrics require."
Though this paragraph refers to the Celebrant, the principles apply also to altar servers:
1. Actions should be performed with the greatest reverence, propriety, and dignity;
2. Posture, movements and gestures should be carried out carefully and in accordance with the rubrics;
3. Efficient, decorous, and reverent actions and speech;
4. No idiosyncrasy, exaggeration, or affectation;
5. Nothing that would distract anyone's attention from the mass;
6. Hands and eyes should be controlled;
7. No irreverence, indifference, carelessness;
8. No excessively pious gestures which fall outside what is prescribed;
9. Movements, looks, and voice, should be disciplined.
The restrained spirit of the traditional mass is characteristic of genuine spirituality in the Roman tradition. Rubrics about voice or movement must be carried out; they must be carried out exactly, carefully, devotedly. They must not be done half-heartedly; they must not be exaggerated. Custody of the mind and of the senses must be assured.
At one time, Catholic priests were renowned for their self-discipline. This was modelled on our Lord and Saviour Jesus Christ, who came not to be served, but to serve. Discipline was maintained through the ethos of the traditional mass, office, mental prayer, and rule of life. It was a tried and tested method for working out the salvation not only of the priests themselves, but of their people also. The charism of traditionalist orders and fraternities today is the same, and they are being blessed abundantly by our Lord.
Altar servers, to be worthy of the name of a 'servant of the altar', should strive after the same spirit: the self-discipline of a true soldier of Christ. Of all the actions we carry out in our lives, those that are carried out nearest to the altar touch most closely on our salvation - let these actions be a model for the rest of our lives also. Words clear and correct; gestures precise, manly, and unexaggerated; discipline of our eyes, hands, senses, words. A true and fervent spirit, which regards more the Lord rather than one's self. A remembering in Whose presence we are, and Who we serve.