Is this the career progression you envision? Jr. Art Director (or writer, account exec. . .) Sr. Art Director > Creative Director > Agency Owner. That's a long way out and most of our career telescopes can't focus that far. But rest assured, it happens. Maybe it will to you.
Every agency owner has a "used to be" story. They used to be a jr. account executive. Or they used to be a sr. art director. And now? Through perseverance, focus, passion, dedication, conviction, and a boat load of smarts, they own the place. They've risen through the ranks (albeit much higher than the average joe) starting out in this business just like you and me. Remember that when you are nervous going into an interview or finding your hand shaking while making a presentation. Everyone in this business was junior once.
If you see yourself owning an agency someday, find a few role models and learn how they made it happen. Take BD'M in Minneapolis. Started a few years ago by three partners who turned the dream of owning an agency into reality. Monday they were named Best Small Agency in the 4A's O'Toole Awards. Three guys, once junior, now owners and making it happen.
Put being new to advertising in perspective. It'll help when you are overwhelmed with trying to find your first job. Or you don't know whether to leave that job to take another. Every person in this business started in the same square one. Every agency was once a couple folks with a dream. Trust that you'll get there.