Exchanges go to great lengths to guarantee your funds are safe. Nonetheless, like any other big store of value, exchange wallets can become targets for nefarious activity. In the context of a long-term investment, your hard-earned cryptocurrencies will be safer in a personal wallet which you control rather than an exchange wallet.
Below you can watch a video by Charles Hoskinson (the inventor of Cardano) on safety tips for keeping your crypto safe.
Both Cardano Wallets we will be talking about later in this guide use a multi-word mnemonic phrase (24 for Daedalus and 15 for Yoroi) to recover your wallet should you loose access to your device (broken, stolen, etc).
Store your mnemonic on paper (a notebook that you will not loose): make 3 copies and keep them in at least 2 separate physical locations.