[jceb81]

It depends on the DID method that you're using. The DID method is kind of the identity management system for Decentralized Identifiers. Many DID methods are based on blockchains and with that there are usually no recovery mechanisms for DIDs in place - if you lose your private key the identifier can't be updated and you can't prove ownership over the identifier anymore which in turn renders associated credentials (see Verifiable Credentials https://w3c.github.io/vc-data-model/) unusable.

Custodial services are a good way out. Another option with DIDs is that you can add more than one key to DID. This way you can have one key that is stored away somewhere safe and is only used for recovery purposes.