A key driver at work is the satisfaction that you get ,when you see your actions adding value to the project.

Think about the difference in levels of satisfaction while ::

Investigating & characterizing a complex bug vs attending a meeting

Writing and executing an automated script to reproduce a problem vs filing up a template

Providing a co-worker or developer test information vs providing formal status reports

taking a judgmental call vs blindly being compliant

test execution with no questions vs questioning the test execution

empowerment vs control

satisfaction vs going through the motions