If you used Outlook, then go to your message in the sent messages folder and open your message. It's been ages since I've done it, but there ought to be a button marked 'options' in the area of the tool-bars. One of the options to choose from on the sent message will be to kill the message which is what you'd want to do. Other mail service programs may offer a similar service, but I'm most familiar with Outlook.
There are no guarantees though, if the other person has their email open or has already read it, there will be no effect. Also, the different mail servers may block that sort of action. The bottom line is that there are no sure ways to kill a message once it's sent. The only way to make certain that a recipient doesn't get a message is to not send it to them.