Maybe you are thinking James Bond, or Jason Bourne, well.... not really.
Having multiple identities can help you organize your online life properly.
I recommend at least two email addresses, one for garbage that doesn't matter, and one for important stuff like business and school. The garbage account is used to get accounts at places you probably won't go back to. You can have both accounts feed into an email client, that way you only have to check your email at one place. Another concept to think about is walling off your accounts by having different password groups, just in case someone fools you into feeding their keylogger, you can slow the damage done to your accounts.
TL;DR use at least two different email addresses, and different sets of passwords to increase security.