Jesus simply says [ to everyone ] that if you ‘travail’ – if you stand under charges, i.e. under condemnation, “come to Me.” When you come to Me, says Jesus, “I shall fulfill you” so that you no longer stand condemned; “I shall refresh you” so that you no longer ‘travail.’
“All ye that travail, and be charged, come to me, and I shall fulfill you [and I shall refresh, or fulfill, you].”
The trick, so to speak, to ‘eternal life’ is as simple as Jesus’ invitation to come to Him. The trick is to realize you ‘travail’ and that “you stand under charges.” Without this simple recognition, going to Jesus is out of the question for the human being is ultimately too proud.
Paul is warned by the Holy Spirit to expect hardships and prison. He writes:
“But I dread nothing of these, neither I make my life preciouser than myself, so that I end my course [the while I end, or fulfill, my course], and the ministry of the word, which I received of the Lord Jesus, to witness the gospel of the grace of God.” (WYC)
“But none of these things move me, neither count I my life dear unto myself, so that I might finish my course with joy, and the ministry, which I have received of the Lord Jesus, to testify the gospel of the grace of God.” (KJV)
“But I count my life of no value to myself, so that I may finish my course[with joy] and the ministry I received from the Lord Jesus, to testify to the gospel of God’s grace.” (HCSB)
However, I consider my life worth nothing to me, if only I may finish the race and complete the task the Lord Jesus has given me —the task of testifying to the gospel of God’s grace. (NIV-1984)
I love the Wycliffe Bible translation! Note that Paul is not testifying about the gospel of the grace of God, but he is witnessing the good news firsthand. He is not counting his life so precious that he dreads imprisonment or hardships. Rather he determines not to “end his course” before he finishes “the ministry of the Word, which [he] received of the Lord Jesus.”
Perhaps the other translations miss this subtlety only slightly — that Paul does not testify about the gospel; but rather witnesses it himself. What Paul works to complete is “the ministry of the Word” which is certainly more than telling others the good news. Paul determines to consider his life worthless in comparison to his calling — for to Paul, to live is Christ and to die is Christ.