As you sit in a comfortable position with closed eyes (preferably after an asana practice), allow your entire mind to concentrate on your breath. Watch your lungs expanding and contracting, feel the breath coming in and out through your nose. As you inhale, imagine the oxygen pouring in through your lungs and out through your veins, renewing each cell of your body. As you exhale, imagine all the toxins and waste that your body doesn't need pulling out from each of those cells, back through your veins and exiting your lungs effortlessly. Your body unconciously renews and restores your body with each breath.
Now imagine that with this inhale of breath also coming strength, peace and positive energy flowing into your body. And with each exhale you release tension, stress and negative energy, simply allowing it to leave you. Imagine these good things flowing into your life and negative things leaving you just as effortlessly and unconciously as your breath.
Just as your body benefits from literal breath more when the air you take in is clean and unpolluted, so it is easier to draw good into your life if your surroundings are calm and positive. The only trick is that sometimes our bodies & minds hold on to stress and resist "exhaling". Today see if you can conciously release negativity and surround yourself with a little more of what you want in life.