There are good reasons for mastering the interplay between the abstract and the concrete. For all of its flexibility and universality, the abstract takes a lot of mental work to render into full clarity. When someone is making abstract arguments, you may find that it takes a strain to follow the arguments, in which you work to keep various symbols in the proper relation to each other, adding more connections and elements, grasping for the meaning of such a structure which relates to the real.
What lends such arguments more power is then anchoring them into the concrete, utilizing various vehicles of metaphor and analogy for their powers of transmissibility, converting concrete particulars into universals, grafting them onto the abstract structure.
Metaphorical concrete-anchored concepts like "hard" and "soft," or "hot" and "cold" take their power from a visceral evocation of direct experiences, which are immediately apprehended by the body in sense and muscle memories. One comes up against something "hard" in one's experience, and one can immediately feel limitation and resistance on the fingers and against one's muscles. One "knows" what it means in one's "bones," as it is often put.
The "concrete" conceptual category is apt, as it allows for a firming up of one's inquiry, establishing a conceptual certainty that one can "stand" on and thrust against without becoming lost in constant draining mental contrasts.
But where the concrete concept loses steam is in its very particularity: hot can cool to cold, and heat to hot again, and soft things can become hard, or hard things soften, and one becomes lost in the perpetual dramas of transformation and movement. The abstract, through its connective relationality, situates those many gradations into "structure," which can more readily be apprehended and understood and organized in the mind's eye, and in turn, anticipated.
