Tell yourself you'll do 20 push-ups in the next five minutes (a specific stretch goal) vs. five push-ups (non-stretch) or the vague idea that you'll do as many as you can.
Since I worked for the Federal government for 26 years starting my own business and a non-profit organization was definitely a stretch outside my comfort zone.
Suddenly we were confronted with seats where one's nose was almost touching the back of the seat in front, and where the ability to stretch out in a reclining position was non-existent.