I came across this letter sent by Adoniram Judson from Burma on June 25, 1932 with some advice for new missionaries coming to the field. Below is some of what he said.
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?
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.
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.
Eighthly. Never lay up money for yourselves or your families. Trust in God from day to day, and verily you shall be fed.
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.