If this is an email address you have used previously, then I would try to back track and think where. If you have emailed friends, family or colleagues, then perhaps you could try asking them if they still have emails from you that they could check?
If it is a brand new account that is not linked to anything- eg. Sign in to websites, and that nobody will be trying to contact you on, then it may be easier to just create a new account.
Other than that, you can try the hotmail/outlook help. I don't think there is a straightforward help topic related to forgetting what your email address is, so you may want to contact one of their help advisers on the "live chat" option of Microsoft Support. They should be able to tell you how to regain access to your account, or may be able to verify other details with you to do it for you.