End-to-end encryption is a type of encryption that ensures data is only accessible by the sender and recipient. As such, if you have forgotten your password associated with end-to-end encryption, it can be difficult to recover as there is no centralized system or third party service that can access the data.
The best way to try and recover a lost end-to-end encryption password is to first look through any records you may have saved related to the account, such as emails or physical notes. If these attempts fail, then you should contact the provider of the encrypted service for assistance in resetting your password. Depending on what type of service it is, there may also be additional security measures in place that will require confirmation from you before allowing access again.