Loosing Faith in my Business Venture...well maybe not

For the past several weeks I've been deciding whether or not my business venture will be a good idea. Yesterday, I felt after talking to my roommate that maybe it wasn't a great idea. Today, I rethought it I just can't imagine this venture being a failure. I just see a great need, plus when I was at that age I would had love this product. I'm not mentioning this product because I don't want to take the chance of someone stealing the idea. Should I keep pursuing the possible business idea or should I just call it quits?