On what the work is carrying

Read as encouragement, the line is unbearable — a demand that you feel something warm about a job you did not choose. Gibran is doing something more modest.

He is saying that care is not invisible. It shows up in how a thing is made, and someone downstream will meet it there without knowing whose it was. The corollary is uncomfortable and he states it plainly elsewhere: indifference is visible too, in exactly the same way.