When you have ten minutes or so to spare, and will be uninterrupted, sit down and follow these instructions;

Breathe.
Close your eyes, inhale a long deep breath, slowly, and then hold it within.
Count leisurely to four.
Slowly, gently, exhale.
Repeat three times.
Do not try to block out any noises around you, let them exist and wash over you, rather than distract.
Now, keeping your eyes shut, picture in your mind a tiny bus in the far distance on the right hand side of your vision, and observe it trundling towards you.
Watch it come closer and closer, then curve to the left and pull to a stop in the centre of the empty space you see before you.
The doors open. Now, take all the thoughts that are spinning around your head and won’t stop, and get them to board the bus, one by one. This will automatically visualise itself. Once they are all packed in tight, bulging out of the windows,the doors shut. The bus then moves off, continuing towards the right hand side of your vision, and then turns again in order to head off into the far distance on the left.
Your mind feels lighter.
Breathe.
Continue to breathe slowly, at a comfortable pace.
Open your eyes.
Smile.