While our experience can't compare with those who lost family or friends or who suffered horrendous injuries, it did bring the reality of terrorism home to us. Anyone, however random, can be a victim and we certainly need to be aware that there are organisations promoting and using terror as a weapon and to take steps to defend our countries and ourselves from it. That said though we also need to not let the threat of terrorism define our lives. The people in London were going about their daily lives and there was nothing they could have done which would have stopped these attacks so there's no reason to assume that retreating to a fortress is going to protect us. In fact, with modern weapons the more we crowd together the more vulnerable we seem.
All we can do is take reasonable precautions and that means international cooperation and funding of programs to combat the scourge of these fanatics within our own communities. The ubiquity of the internet means we are often not aware - even within a family - of what is going on behind closed doors so we need to work actively at engaging with those who are at risk. With so many like those who perpetrated the London bombings being home grown, we need to be watchful and aware of potential threats but, while that is difficult, the answer is not to give in and give up our cherished way of life.
We certainly must be vigilant but we must also not let our reasonable fears turn into unreasonable ones and bring in laws that alter or take away long established rights in the belief it will protect us. As soon as we do this we are actually playing into the hands of these terrorist organisations. They win when they have affected the way we live our lives by letting our fear change us. Yes, we need to be aware that there is great danger and that these people are ruthless and vicious in their pursuit of their aims but we must not give in to their threats. As soon as we do that they've already won.