If you don't remember a password, you can change it. To change the password of one user, use SET PASSWORD FOR user = 'newpassword'.
You are the InfluxDB administrator
Here's an exemple :
You created a new user : bruce, but you did a typo mistake on the password :
CREATE USER bruce WITH PASSWORD 'iambatmon'
You can change the password by doing
SET PASSWORD FOR bruce = 'iambatman'
You are not the InfluxDB administrator
You need to stop the influxdb service
service influxdb stop
Change auth-enabled = true by auth-enabled = false
Then, restart the InfluxDB service
service influxdb start
Then go back to You are the InfluxDB administrator, because no authentification is needed to access the InfluxDB administration
Then don't forget to set auth-enabled to true and restart the service