In 1832 Adoniram Judson wrote to the Foreign Missionary Association of the Hamilton Literary and Theological Institution, NY. In the letter he gives 10 points of advice to missionary candidates. They are as follows:
In commencing my remarks, I take you as you are. You are contemplating a missionary life.
First, then, let it be a missionary life; that is, come out for life, and not for a limited term. Do not fancy that you have a true missionary spirit, while you are intending all along to leave the heathen soon after acquiring their language. Leave them! for what? To spend the rest of your days in enjoying the ease and plenty of your native land?
Secondly. In choosing a companion for life, have particular regard to a good constitution, and not wantonly, or without good cause, bring a burden on yourselves and the mission.
Thirdly. Be not ravenous to do good on board ship. Missionaries have frequently done more hurt than good, by injudicious zeal, during their passage out.
Fourthly. Take care that the attention you receive at home, the unfavorable circumstances in which you will be placed on board ship, and the unmissionary examples you may possibly meet with at some missionary stations, do not transform you from living missionaries to mere skeletons before you reach the place of your destination. It may be profitable to bear in mind, that a large proportion of those who come out on a mission to the East die within five years after leaving their native land. Walk softly, therefore; death is narrowly watching your steps.
Fifthly. Beware of the reaction which will take place soon after reaching your field of labor. There you will perhaps find native Christians, of whose merits or demerits you can not judge correctly without some familiar acquaintance with their language. Some appearances will combine to disappoint and disgust you. You will meet with disappointments and discouragements, of which it is impossible to form a correct idea from written accounts, and which will lead you, at first, almost to regret that you have embarked in the cause. You will see men and women whom you have been accustomed to view through a telescope some thousands of miles long. Such an instrument is apt to magnify. Beware, therefore, of the reaction you will experience from a combination of all these causes, lest you become disheartened at commencing your work, or take up a prejudice against some persons and places, which will embitter all your future lives.
Sixthly. Beware of the greater reaction which will take place after you have acquired the language, and become fatigued and worn out with preaching the gospel to a disobedient and gainsaying people. You will sometimes long for a quiet retreat, where you can find a respite from the tug of toiling at native work — the incessant, intolerable friction of the missionary grindstone. And Satan will sympathize with you in this matter; and he will present some chapel of ease, in which to officiate in your native tongue, some government situation, some professorship or editorship, some literary or scientific pursuit, some supernumerary translation, or, at least, some system of schools; anything, in a word, that will help you, without much surrender of character, to slip out of real missionary work. Such a temptation will form the crisis of your disease. If your spiritual constitution can sustain it, you recover; if not, you die.
Seventhly. Beware of pride; not the pride of proud men, but the pride of humble men — that secret pride which is apt to grow out of the consciousness that we are esteemed by the great and good. This pride sometimes eats out the vitals of religion before its existence is suspected. In order to check its operations, it may be well to remember how we appear in the sight of God, and how we should appear in the sight of our fellow-men, if all were known. Endeavor to let all be known. Confess your faults freely, and as publicly as circumstances will require or admit. When you have done something of which you are ashamed, and by which, perhaps, some person has been injured (and what man is exempt?), be glad not only to make reparation, but improve the opportunity for subduing your pride.
Eighthly. Never lay up money for yourselves or your families. Trust in God from day to day, and verily you shall be fed.
Ninthly. Beware of that indolence which leads to a neglect of bodily exercise. The poor health and premature death of most Europeans in the East must be eminently ascribed to the most wanton neglect of bodily exercise.
Tenthly. Beware of genteel living. Maintain as little intercourse as possible with fashionable European society. The mode of living adopted by many missionaries in the East is quite inconsistent with that familiar intercourse with the natives which is essential to a missionary.
For the entire letter, see here.