Start off at your own pace and do what you feel comfortable with at first. As you get more into it and more comfortable then start pushing yourself a little at a time.
Bill is right that you might not be going fast enough which may affect your balance. Also the slicks that Mr. Beanz suggested will make a world of difference. Since you are new to riding on two wheels give yourself time to adjust. Its different for everyone as far as how long it takes but just stick with it.