If you keep telling yourself "I'm not smart enough", long enough, all you'll have in the end, is an excuse. At your age, you don't know what you don't know, or need to know.
There are far more people that wish they had pursued a degree than those who regret getting one. Especially facing the the changing job market and economy thats coming down the pike...Do yourself a favor and take the advise given here by the majority and get a degree.