Junior year you grow deeper; deeper in your relationships and more deeply involved in your studies. If it hasn't already, school will likely feel overwhelming. However, the study skills you've developed in your first two years and the friends you've made in and out of class will help you pull through the tough times. Classes will be specific to your major and will really open your eyes to your area of study.
Despite the seemingly insurmountable amount of work and activities you'll be involved in, you'll find time to give back as well. If you're involved in student clubs or organizations, you'll be encouraging freshman to join or helping to organize events. As a Junior, you'll have established your priorities in college and will invest heavily into those areas most important to you.