Isn't it ironic how your productivity goes down if you're too stressed? Ironic 'cos when you're very stressed, it's usually 'cos you need to complete something fast or need to do something excellently.. and that's when you'll need your productivity to go up instead of it going down.
vicious cycle ah? need to finish work by a certain dateline --> inability to concentrate+low productive levels+ avoidance symptoms --> greater need to finish work by a certain dateline --> more behavioural and emotional manifestations of stress --> so on and so forth.
it spirals down and down and down instead of lifting you out of the situation :)