How does the analogy of the gem and the stone explain a disciple's role in their own spiritual development?

The analogy of the gem and the stone, found in Chapter 19, clarifies how a disciple's inner disposition affects their spiritual progress, even under the same Guru. The text explains that both a stone and a gem are polished on a whetstone using the same process. However, while the stone merely becomes smooth, the gem transforms into a "brilliant jewel." This illustrates that although the Guru provides the same guidance and grace to all, the outcome depends on the disciple's inherent nature and readiness. A disciple with strong faith and patience, like the gem, can be transformed into something brilliant. Another, lacking these qualities, may receive the Guru's influence but will not achieve the same profound transformation, highlighting the disciple's active responsibility in their own development.