time is like liquid in a bottle

time is like liquid in a bottle.
liquid is not too compressible (cf. air).
if a bottle is already filled with Coke to the brim, there’s no layman way to introduce (choose any favourite drink, e.g. Pepsi, 100-Plus, Kickapoo, 佳佳凉茶, whatever)

(source/acknowledgement: thedieline.com)

to introduce (insert favourite drink) into the bottle, some Coke must give way.
to introduce new practice into any teaching and learning context, some old practice must give way.

time is like liquid.
time is incompressible, and limited.