As life in general becomes safer, these incidents stand out far more.
In the past people used to die in industrial accidents, diseases were more prevalent, life expectancy was shorter and there were more deaths through conflict.
Our society is becoming very risk averse, with a tendency always to look for someone to blame for everything.
Whilst I do not mean to make light of what hapenned, and I sympathise with those affected, we still need to keep things in perspective.
There is no way really to be safe, but the level of risk is rather low.
Although common sense should apply, in general I see no reason to modify my life. And I certainly do not worry about it.
The threat from the IRA was far higher, IMO.
As soon as one group fades, another rises to replace it.
Places which are seen to be safe, are just places where nothing has happened yet, but are just as risky. Sharm el Sheik proves this - it was considered safe, since no-one had attacked it. This just means that it is a soft target.
Places which have just been attacked are seen as more risky, when IMO they are less so, since places are not often attacked twice. Just because some time passes, it does not mean that the risk is reduced, i.e. people are vigilent for a short period then become complacent when nothing happens for a while. It is when people become complacent that the risk rises.
In general people do not judge risks well.