At the last workshop I went to, Sifu Chin gave a metaphor about the training process which managed to stick with me:

If we view I-Liq Chuan skill as a physical building, then the skill is not built on a central pillar supporting everything.  It’s the combination of many pillars which support the walls and roof.  Mindfulness forms the foundation upon which everything else can be built.  Training proficiency in the individual elements of the system erects the pillars and builds up overall skill.  The sum of the pillars builds a strong framework for supporting the walls and roof.  Neglecting elements of training leads to gaps in the support structure and weaken the building.

Attaining skill in most endeavors will involve similar training several interrelated subskills.  Athletes need to train speed, power, strength, and agility, as well as numerous skills related their sports.  Musicians need to grasp timing, pitch, the technical aspects of playing their chosen instrument, and how to translate the physical playing of the instrument into a moving musical expression.  Skill comes from the sum of proficiency in many sub-skills, not just from mastery of a single element.