The world is driven by self-preservation and self-promotion. Individually, the natural man is guided by self-serving motives. This should not be true of saints.
It is always right to do right, but it is more perfectly right to do right for the right reasons. In other words, serve the Lord, but do so out of a pure motive.
One must choose his reward for actions taken. Would he rather receive eternal reward from God the Father, or temporary praise and recognition from his peers?
How would making your motive match the Lord's motive change how you approach the Christian life (from witnessing to praying to Bible reading and so on)?
The context of our passage shows the disciples gathering some food while the Lord dealt with a Samaritan woman alone. When the disciples returned, the woman left to tell others she had found the Christ. The disciples were confused when they saw the Lord talking with a Samaritan woman. They immediately seemed to focus on His physical needs and begged Him to eat. To their shock, the Lord suggested that He had meat to eat that they knew not of. What was this meat to which He referred? His meat was to do the will of His Father (i.e., mend broken lives). The Lord instantly turned the disciples’ attention toward the harvest, only the harvest involved the souls of men rather than earthly sustenance. Christ pointed out that the time to labour was not some future date, but here and now. The fields were already white to harvest. There was no time for excuse or delay. Now was the time for diligence!