To grow in confidence in a new situation as one gains experience.
let the grass grow under one's feet
To dally; to fail to make progress.
grow a pair
To be brave; to show some courage, especially in a situation in which …
grow some balls
To be brave; to show some courage, especially in a situation where one…
vote with one's feet
To express one's preferences through one's actions, by voluntarily par…
get one's feet wet
To begin gaining experience; to tentatively try something new.
large and in charge
Dominating or controlling a situation with confidence and aplomb.