. Zen Keys provides practical applications for Zen philosophy and is a great tool for learning how to blend mindfulness with the fast-paced nature of the modern world. I picked these quotes because they apply directly to day-to-day life. They're not extreme, and don't talk about saving the world or doing anything extravagant. They focus on what you can do today, and how you can help yourself and those around you.
"People have a hard time letting go of their suffering. Out of a fear of the unknown, they prefer suffering is familiar."
Strangely enough, after a long enough time experiencing suffering, we get used to it. We start to fear eliminating suffering. If you're feeling bad, ask yourself why. Most of the time, we suffer merely because we think we're supposed to. It doesn't have to feel that way; like I wrote earlier in the week: happiness is a state of mind, not a goal to be achieved. Letting go of suffering is something you can only do internally; you can't always rely on outside sources.
"Mindfulness helps you go home to the present. And every time that you go there and recognize a condition of happiness that you have, happiness comes."
Suffering comes from the past and future, usually. These worries make up most of our problems. Living in the present negates suffering and allows us to appreciate where we are and what we're doing right now, without worrying about what happened or what's next. Appreciate what you're grateful for right now, and happiness will follow.
"Every thought you produce,
anything you say, any action you do,
it bears your signature."
Part of mindfulness means always being self-aware. The things we say and do reflect us, so it's important to try to think/act harmoniously with your true nature. Don't pretend to be someone you're not. 
"When you love someone, the best thing you can offer is your presence."
This one is especially applicable to the 21st century. We've all heard about 'text-message break-ups' and even 'sexting'. These are mostly things naive teenagers do, but the vast majority of us still communicate online daily in some form. I'm doing it right now, writing this. It's easy to get caught up in thinking virtual communication is the equivalent of spending time with a person. If you find yourself relying too much on facebook or texting, try to personalize your interactions more. Invite someone close to a coffee date or go on a walk with them as a way of replacing a would-be facebook post or a tweet. Modern technology has its benefits, but people are meant to appreciate each other face-to-face, not screen-to-screen.
"Freedom is not given to us by anyone; we have to cultivate it ourselves.
It is a daily practice."
Another product of modern technology is massive amounts of information. People know far more now than they did 100 years ago. As a result, we often blame our personal problems on big things, like government and politics. Sitting in my house, if I wanted to, I could choose to feel like a 'slave to the system', or buy into some crazy conspiracy theory. In reality, freedom is individualized. I must work to cultivate it, like Thich Nhat Hanh says. Mindfulness leads to freedom because it allows us to think for ourselves. 