Lapidarist... only lapidarists can know the value of a stone.

 Lapidarist who polishes a stone and makes it a diamond... And a true lapidarist can make any stone diamond.

Similarly, a good teacher can identify the student of her/his field of talent. A teacher has a larger role in shaping the life of a child.

To overcome inertia... For the start Quantity is to be considered and slowly Quality comes automatically.

 Just try to express it completely... At the start just don't concentrate on anything. Just complete with any random text, words.. but just complete for the sake of completing.  Quantity should be considered at initiation to overcome the inertia... later, later, much later slowly concentrate on quality....In fact after some time quality comes automatically... Quantity is in our control but quality should be automatic.

Quantity: giving speech for 30 minutes continuously... writing an essay of 1000 words...