If you already started the job, and worked at least 10 minutes, 30 minutes or 1 hour, it will generate a report for that worked time, and give back the energy for the remaining interval. The motivation drops corresponding with the time worked in the report.
For example, you schedule a 2h job, cancel after 1h40m. The report is generated for 1 hour worked. You get back 12 energy, the motivation drops only by 3 points. It's like you worked for 1 hour, than sit idling for 40 minutes.