A new study has uncovered what may be the secret ingredient of entrepreneurship: euphoria. In a nationwide survey of 3,000 entrepreneurs with businesses less than 18 months old, one-third of the respondents rated their chances of success as 10 out of 10. Curiously, their level of optimism bore no relation to their degree of preparation, according to Purdue University professor Arnold Cooper, who is conducting the three-year study under the sponsorship of the National Federation of Independent Business.