British English has many phrases for keeping something in reserve.
Belt and braces: Using two safeguards where one might do. Braces are straps that hold up trousers.
To save for a rainy day: To put money aside for hard times.
To hedge one’s bets: To keep more than one option open.
Don’t put all your eggs in one basket: Do not let everything depend on one plan.
Ne’er cast a clout till May be out: Do not put away warm clothes until the end of May. A clout is an old word for a piece of clothing.