"written in stone"という表現をご存知でしょうか？
The doctor told me I have taken down every medical report on the life expectancy of the kind of cancer I have. The usual expectancy is two to three years, I'm on 13 years now, and they don't know why, and they don't know what I'm doing different.
They are one of the main reasons, I'm still here to help others realize it's not written in stone. Things can be changed, but you have to do your share too and you have to give up some things but you can fight this or anything life throws at you, don't just sit and take it. Do something about it.
(Kathy Golemiec. Realize things aren’t written in stone. NG News. January 7, 2016.)
it's not written in stone.
Things can be changed...
この成句は、"not set in stone"とも表現されることがあります。Collins Cobuild Dictionary of Idiomsの定義では、下記のようになっています。
If you say that something such as an agreement, policy, or rule is not set in stone, you are pointing out that it is not permanent and that it can be changed.
HOW TALL WILL YOUR CHILD BE? THIS FORMULA ISN'T CARVED IN STONE, BUT IT DOES seem to be relatively successful at predicting adult height. For girls: Subtract 5 in. from dad's height and keep mom's height constant - your daughter should fall somewhere between the two. So, a girl born to a father who is 5 ft. 10 in. (178 cm) and a mother who's 5 ft. 7 in. (170 cm) should grow to somewhere between 5 ft. 5 in. (165 cm) and 5 ft. 7 in. (170 cm).
(Today's Parent. 2005.)
"written (carved) in stone"とは、恐らくは石碑などに刻まれた文字のことを言っているのだろうと思われます。石碑に刻まれた文字が遠い過去の事実の記録として、不変の事実として見做されるように。
She was fired, she says, for being pregnant. One week before she was due to give birth and go on an eight-week pre-approved maternity leave, her boss announced she was being permanently replaced " because of the length of time the position would be vacant." "You can't believe how angry I am," says Soreo-Yasher, whose family has been struggling to make it without her $ 35,000 salary. "If you're going to have a family, you better make sure it's written in stone somewhere that you will get your job back. Because they can do this to you."
(USA Today. 1991.)