Here I thought of tension as stress and overworking. This picture also reminds me of a 'tension headache.' The concept of tension is more literal here than my first example. Tension can be though of in two ways. Dictionary.com defines tension as "The condition of so being stretched; tautness." Therefore, overworking can lead one to overstretch their abilities. Tension was also defined as "Mental, emotional, or nervous strain" which is what happens when one is under stress for long periods of time. And jobs and working are one of the main causes of stress.
[picture is from sxc.hu]