If you've registered an account via email, you can quickly restore your password at any time.
Every single one of us has been at the point where you can't recall the password from your account. There's nothing to worry about. If you've registered an account via email (and not using your social networks), you can restore the password in a couple of clicks.
Or you can:
Run the app on your iOS device;
If you're not logged in, you'll see the login window with the "Forgot Password?" link below it;
Use the "Forgot Password?" link to request a password restoration.