You will get more done and you will feel better doing it. Make sure your workstation is set up to reduce fatigue. Re-adjust your chair between each work task. Check your posture to make sure you are not slumping. Take an inventory of what feels tight or sore on a regular basis.
Chances are that a sore area needs to be stretched.
It does not take much time to release built up stress. Take a refreshing exercise break. Pull your shoulders down and gently lower your ear to your shoulder each way. Hold for a count of five. Repeat three times.