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.