When creating a new profile, you can specify an e-mail address. We will then send a verification e-mail to this address. In this e-mail, you can click on a link to verify your profile, after which your successes as a player will be permanently backed up.
Because this e-mail sometimes gets lost, you can request it from within your profile in the game. To do so, click on My Profile or on your avatar and scroll to Personal Data. You will only see the Secure button if your profile has not yet been verified.
Further info about this can be found here.