Aristarchus, my fellow prisoner, greets you, as does Mark, Barnabas’s cousin (concerning whom you have received instructions: if he comes to you, welcome him), and so does Jesus who is called Justus. These alone of the circumcision are my coworkers for the kingdom of God, and they have been a comfort to me. (Colossians 4:10-11 HCSB)
"These Alone of the Circumcision" (Jews) Paul was a Jew among Gentiles. He was a man of vast learning among a sea of people who were ignorant of the life, culture and way of Judaism. Some were following him, some were fighting him and some were sharing the load with him (three to be exact). It is not good to be alone in the mission field. Paul was called and glad to be on mission but needed the encouragement of others to get the work done. Not just any others. Paul found value in the company of those he could connect with who already got him. Those who already understood his plight without the need of much exhausting explanation.
We all need some people in our lives that already have the comfort we need because they have been where we have... or further. Those who are outside the life and culture of Christ or those who are new to it and have minimal understanding of the life in Christ cannot always bring to you the relief you need. You need someone alongside that is like you already and can strengthen you and give you the comfort you need for the Journey. You need a small community of people who are where you are and in whom you find strength to continue and say "they have been a comfort to me."