You don't have to remember your username, as you can use your email address to log in. Either will work.
Ask for advice
If all else fails, you can always send us a message through the website, and remember to let us know what the problem is in the comments.
Do something different
If you've forgotten your email address - then we're both a bit stuffed - so the best advice would be to go and make a cup of tea and see if it comes back to you.