Sit quietly somewhere, close your eyes, and let everything that stresses you come to mind. It could be anything from years ago, to what happened in the office yesterday.
Write them on a list.
How many hours a week are you working? How many times a month do you visit family? When was the last time you saw and spent time with your close friends? Exercise? Time spent alone thinking, or just resting? Make a commitment to do less of the things that don’t make you happy, and more of the things that do. Few of us on our deathbed wish we had spent more time in the office!
Dedicate 15 minutes a day to clearing each stress on the list. Reserve the same time each day for dealing with a single issue. Within a month you will have sorted the majority of your 'stuff'. Change your habits and your life will change too.
It’s much easier to shift the practical, physical things around. Take that Vitamin D daily; book two sessions a week in the gym.