Every profession has them, the big annual conferences.
Whether it's the national meeting in the metropolitan convention center venues, or the regional meetings that are closer and easier to reach, you've likely been to at least one.
Meet some new people at the next one.
Most attendees either cluster with the normal work colleagues who traveled with them or hang out with the few people they already met from some other meeting or previous work colleague. What a missed opportunity.
You already know those people. It's unlikely you will learn anything new and exciting by spending all your time with them. Meet new people.
How do you break out of your shell?
Meal times are great. Sit at a table that is not full. "May I join you?" Unless the seat was legitimately being saved for someone they will assuredly say yes. Introduce yourself. Pay attention to their names. Say it back to them as you shake hands. Ask where they are from. Make the conversation about them.
Exchange cards. Look them up on LinkedIn. Send them a connection request. You will be surprised at the things that will open for you because of this. Business leads and job opportunities are common. At the very least you will make a new professional friend.