It's the most frustrating sport there is, yet also the most rewarding, in too many ways to count. And the best way to approach it is with the Nike cliche: Just Do It. There is nothing like a bike race, except a bike race. Many people approach it very tentatively, or want to feel like they will be competitive before they do their first race. Unless you are extraordinarily gifted, you will not be competitive in your first race, and the more you race, the more competitive you will become. It's a big learning curve - the sooner you start climbing, and the more climbing you do, the better you become.
Congratulations on what you've accomplished!