得心应手
As clay in the hands of the potter.
Get into one's stride.
Take to something like duck to water.

eg：For you to teach the primary school is as clay in the hands of the potter.

中英俚语俗语来源：“庄子·天道不徐不疾，得之于手而应于心。”

反义词：徒劳无功 To be a fool for one's pains.