You're a little tired this morning. Perhaps you stayed up a little later than usual last night. You have a lot of work to do. So, you decide to have a cup of coffee.
and maybe just one more.
I might as well finish the pot.
Fresh pot? Sure, I'll have some.
Now, you are shaking. Your mind is racing. High anxiety. Paranoid. You can't sit still. You start pacing the floor. You can't keep your mind trained on one single thought. Why did I have that last cup! You feel like your heart is going to explode.
Yep, you've got the jitters.
It's quite a horrible feeling. The only cure for it is time. Take a walk... drink some water... talk to some co-workers or friends. You're not gonna get any real work done now anyways.