What to do when you lost password or username?

Well. Do not panic! look just above this message, and there you see two questions:
Forgot your password?
Forgot your username?

Clicking either one of these will get you to a form that will provide solutions for these problems. (You will be sent emails with the necessary login data. All this works automatically, so you will not bother anyone else; no one will even know that you lost these data.)