Devise Token Auth ships with intelligent default wording for everything you need. But that doesn't mean you can't make it more awesome. You can override the devise defaults by creating a YAML file at config/locales/devise.en.yml and assigning whatever custom values you want. For example, to customize the subject line of your devise e-mails, you could do this:
en:
devise:
mailer:
confirmation_instructions:
subject: "Please confirm your e-mail address"
reset_password_instructions:
subject: "Reset password request"