If you've just run 10,000 metres, it's understandable you'd want to take your foot off the gas.
But at least wait until you've crossed the line or as Molly Huddle found out, it could have devastating consequences.
The American runner was competing in the 10,000m final at the Athletics World Championships in Beijing and looked to have secured the bronze medal.
With Vivian Cheruiyot of Kenya and Ethiopia's Gelete Burka already over the line, Huddle had third place assured and was so delighted with the result that as she reached the line, she raised her arms in celebration.
Only she did it too early, and compatriot Emily Infeld was able to sneak in and take the third place medal.
Huddle looked utterly shocked - and furious with herself - before mustering the sportsmanship to congratulate Infeld.
With the medal winners off celebrating, Huddle appeared to be fighting back tears at the Bird's Nest stadium.