Sensible people, who I believe are in the majority in the UK, understand that any threat there may be from would-be terrorists is comparatively remote (that's 'remote' as in "You're more likely to be hit by a vehicle when you're crossing a city street than you are to be involved in a terrorist attack"), but they understand, too, that they need to be aware of, and alert to, that threat in exactly the same way as they need to be aware of, and alert to, the danger of being run over when crossing the road.

Being aware of, and alert to, a danger is not the same thing as shitting bricks with fear of that danger. Normal people understand the difference, and simply go about their lives - albeit with an enhanced awareness and alertness - despite the fact that the gutter-press, e.g. The Sun and The Daily Mail, constantly squeal about 'imminent terrorist attacks' and fascist, racist politicians like The Trump tell their public that certain countries are 'not safe' to travel to.

My wife travels frequently within Europe for work...her itinerary hasn't changed one jot in the aftermath of the Brussels attacks. She tells me she will, as always, be observant and careful, but she will not be deterred from travelling. Business as usual.