"You'd be worried somebody would pick on them and they might get hit, you know beaten up. You just have to be careful like that. Even though there's a military ceasefire there's not a ceasefire of other sorts."
Although peace may have arrived in Northern Ireland, many ancient quarrels remain unresolved and there is still a lot of bigotry. As the teenager's comment shows, there are many unwritten rules which are well understood and have to be carefully observed.
Most of these things are pretty much invisible to outside observers, who look at Belfast city centre and see people mixing freely and in an apparently relaxed fashion, enjoying the sun and the benefits of peace. The ceasefires have certainly lightened the atmosphere in many ways, but the basic sectarian grammar remains untouched.
The most obvious changes over the past year have been the sudden cessation of shootings and bombings and the consequent easing of security force activity. Police officers no longer have to check under their cars each morning for Semtex boobytrap devices, and in their Land-Rovers they no longer need fear rocket or mortar attacks.
Shoppers no longer have to worry whether parked cars have bombs concealed in the boot, or have to undergo searches on entering stores, or have to endure traffic queues as their vehicles are checked.
Most city and town centres no longer have barriers to keep out the bombers. Parking is easier, and the black-uniformed civilian searchers have been paid off. In most areas, soldiers have disappeared from the streets.
Instead of troops there are now tourists. There always were some holiday visitors, even at the height of the troubles, but now many more are now in evidence. There are back-packers aplenty, lots of foreign students and some older couples.
Not everyone in Northern Ireland was prepared for the influx, and not all the tourists know what to expect. On Sundays, tourists can be seen wandering around the city centre unsuccessfully looking for something - anything - that is open, apart from churches. In a home bakery lately a French couple could be seen seeking croissants and being baffled by soda farls and Belfast baps.
But the locals have been surprisingly welcoming, and from the Republic have poured thousands of visitors, many of them crossing the border for the first time. Many shops now carry the sign "Pounds for punts," signifying that they accept southern currency.
There has also been a new flow in the other direction, with many Protestants venturing south to explore a country they previously avoided. Southern hoteliers and guest houses report a stream of what a Galway hotelier described as "a type of northern visitor we have not seen before".
The biggest changes to lifestyles have taken place in the hardline ghettos, for example in the tough areas of west and north Belfast whose streets were always the most violent. There is no longer heavy military patrolling here: on the Falls Road last week, four policemen could be seen sauntering along without tunics, flak jackets or military escort.
But the ghettos are still ghettos, with high unemployment, an often demoralised community and a large proportion of their young men in prison. The ceasefires have made a great improvement but many problems remain and economic and political alienation persists.
They are also still strictly segregated, particularly in Belfast. The ceasefires have meant some roads that used to be blocked off are now open again, at least during daylight hours, but formidable peaceline walls still criss-cross the city. Most people accept that they will be there for years; some predict they will be there for ever.
Belfast's own brand of apartheid, much of it voluntary, has been in operation for decades and looks set to last for decades more, for there is segregation, in varying degrees, in most schools and many districts and workplaces. The segregation existed before the troubles but was made much worse by them, and will be a continuing feature of life.
With the ceasefires, a start has been made on the road to wards a more conventional existence and for most life has brightened appreciably but the old divisions will be a long time dying.
Tomorrow: The Army adapts