Most city folk have stressful lives - tough jobs, long days, egotistical bosses, busy social lives, irritating commutes, limited to no down time and possibly kids .... Who wouldn't feel stressed!
Active stress management isn't about giving all that up and going to live on a Kibbutz 'Eat, Pray, Love' style, however appealing that may be. Instead it's about accepting what can't be changed about your life whilst changing what you are in control of to make it less stressful.
For example, you might not be able to change the fact you work long hours but you can reduce the stress of it by not committing to early evening plans that you may be late for or have to cancel. Instead make plans later and if you can then leave nice and early make the most of it with a quick gym session or a bit of shopping beforehand.
Are you weighed down with your personal to do list? Rather than ruining your evenings trying to clear it, once a month schedule a relaxing Friday night in and then get up earlyish on Saturday morning and power through your list. Once you've made a good dent you'll feel more relaxed for the rest of the weekend. Whatever you do don't make the mistake of leaving chores til Sunday night, that's a terrible way to start the week!
Maybe your commute is stressful because you have to change at a busy tube station (Bank in rush hour is a real blood pressure riser). Can you take a different route or just get out and walk the second part of the route. Would the bus or boat be less stressful, even if it takes a bit longer it'll be worth it if you don't arrive home harried and grumpy.
It's obviously impossible to totally eliminate stress from a city life and this is why it's also key to put in your diary time for active relaxation. This is in contrast to passive relaxation - collapsing exhausted on the sofa at the end of the day. Instead it's scheduling some regular 'me time' where you switch off from day to day life and just do something enjoyable and relaxing. This could be for 10minutes a day (a relaxing bath, 10minutes of meditation or deep breathing or doing a face pack whilst you have e a cup of tea), for an hour a week (yoga class, massage, facial, spa experience, long relaxing walk in the park) or for a day a month (full spa day, relaxing weekend away, or just a day at home ignoring your to do list and watching old movies and pottering). Whatever you do try and be regular about it.
This kind of proper down time gives your nervous system a break by not stimulating it with the high brain activity associated with working or worrying about something. Whilst it might seem miles away when you're dashing around at work, over time active relaxation will help reduce the impact of this stress on your health and help you lead a happier longer life.