Have you tried any sort of breathing exercises? Whenever I couldn't focus on work i would just take a couple of minutes and do these, and it would help calm me down and renew a little of that focus i was missing.

You can do these without anyone even knowing you're doing then.

- Exhale completlely through your mouth, making a whosh sound.
-Close your mouth and inhale quietly through your nose until a mental count of four
-Hold your breath for a count of seven
-Exhale completly through your mouth, making a whosh sound to the count of eight.
This is one breath. Now inhale again and repeat the cycle three more times for a total of four breaths.

The ratio of this is 4:7:8. If you are having trouble holding your breath for that long then you can shorten the time, but just keep that same ratio. I hope this helps... it might take a couple times practice before you start to notice it (thats what i found) ... but it does after a while!

Hope this helps!