I started practicing meditation a few years ago, to help me deal with anxiety and depression. I used to wake up in the night in a panic, and lie in bed for hours, worrying. I'd spend my days imagining terrible outcomes to situations. I would have panic attacks. I lived this way for a long, long time, just trying to make it through life. People would tell me, "just stop worrying so much! Relax!" Those non-anxious people meant well, because they could not imagine what was going on in my hypervigilant mind.
I turned to meditation as a way to alleviate this constant struggle to feel better. The practice has given me so much; most importantly, the ability to get some distance between my thinking patterns and emotional reactions. This spaciousness is a huge relief.
My mind is still somewhat wired to imagine the worst, but I am much less involved in the storylines that get created.
To keep feeling these positive effects, I try to practice daily, which involves sitting for 10-30 minutes. And, I practice on the streetcar on my way to work.
I am a big fan of (and student of) Shinzen Young and his Unified Mindfulness system, which is a secular system of mindfulness. Shinzen defines mindfulness as three attentional skills working together: concentration, sensory clarity, and equanimity. He gives really clear instructions on how to practice. You can take his course Core - Unified Mindfulness, for free online.
I have been facilitating weekly mindfulness groups for the past couple of years in Toronto and I am working on new ways to help bring the practice to others. Fundamentally, I believe that practicing mindfulness helps us to know ourselves better, and that positively influences our behaviour, and that helps the world.