Continue on as you might otherwise. Donate as you can; assist in calls for volunteers where you think you might be able to help. Our leaders have enough to do now, and our going about our way quietly not only relieves our leaders from being distracted but also denies the terrorists what they want: terror, and a change in our ways.
But mostly, remember this time. Never forget it. As you grow older and assume the challenge of running society, reflect back on what you're seeing and feeling today, and let that be a guide to your actions in the future when you're voting for your government.