Was heißt »aushärten« auf Englisch?

Das Verb »aushärten« lässt sich wie folgt von Deutsch auf Englisch übersetzen:

Synonyme

Being active does not always depend on age.
When I was your age, I was already working.
He has a quick temper.
When I was your age, I cycled to school and back every day.
He's not allowed to vote because he's not of age yet.
He's not allowed to vote because he's not yet voting age.
He was orphaned at a young age.
No one lives to the age of two hundred.
I began playing tennis at the age of 14.
I began to play tennis at the age of fourteen.
What is the elephant's age?
She began dancing at the age of eight.
My form teacher is the same age as my mother.
I grant there is no strength in old age.
Old age is rather talkative.
Indolent youth creates a begging old age.
Your uncle is pretty attractive for a man his age, and I'm sure at the senior center he's a babe magnet!
"I already had a boyfriend when I was your age." "Ugh, Mum! Boys are totally disgusting!"
I've got an older brother the same age as you.
People my age usually don't watch as much TV as older people do.