What is a successful missionary? I think that the answer that pops out is one who has a bunch of salvation decisions and baptisms. Could be one who goes to where there is no church and starts one and it eventually results in having all kinds of programs and maybe a Bible institute, orphanage or any number of ministries.
I think that the command to be faithful would probably be the clearest sign of a successful missionary. But I also think that it is more than that, because I think that you can be faithful in that you are on the mission field, but not necessarily faithful in getting work done. A successful missionary will actively be working towards making disciples. But I think that there are also many stages to this including plowing (working on people who have never even heard of Jesus or are totally against Him), sowing the seed of the Word of God through evangelism, reaping by seeing people saved, and growing or discipling them which is a long process of seeing believers mature in the faith, be leaders in churches and even be Pastors or be sending out missionaries. There are so many aspects to the process of making disciples that limiting the definition of a successful missionary to one who sees lots of decisions is hard to do.
What do you think?