When you create a wallet address, you also create a seed phrase. With one significant exception, a seed phrase is similar to a banking pin in that it gives you access to your wallet and your token allocation. Unlike a pin, if you lose your seed phrase, you can never access your wallet or your token allocation ever again.
Warning: Losing a seed phrase is final and destructive. Blockstack does not keep a copy of your seed. Blockstack cannot give you a new seed, get your access to your wallet, or return your tokens if you lose your seed phrase.
Keep your seed phrase secret. Just as with a banking pin, anyone that knows or steals your seed phrase can access your allocation.
You should write your seed phrase down and store the paper you write on in at least two secure locations. A safe or lockbox is a good location. You can also store it online in an encrypted password manager such as 1Password. You should never simply store a seed phrase in Apple Cloud or Dropbox.