In his first career MLB at-bat, Dustin Peterson tried to walk after just three balls

You can't overestimate how stressful a big league debut is. After decades of hard work and dreams, you've finally received your chance. Your friends and family -- along with thousands of fans -- are watching. You have brand-new co-workers that you want to impress. And, to top it all off, Monday's second game of a doubleheader between the Mets and Braves didn't end until after 1 a.m. ET. 
So, when Braves rookie Dustin Peterson strode to the plate for his first big league at-bat in the bottom of the ninth with two outs and Atlanta down by 3, you can imagine there was a lot going on in his mind. Which probably explains why he thought he had drawn a walk on just three balls from Jeurys Familia. 
You can see that Peterson even did the rookie's supplication by immediately putting his head down and walking to first before realizing his mistake: 

You can almost hear the record scratch, as Peterson goes in reverse back to the box. 
Unfortunately for the rookie, the at-bat would not end in his favor. He struck out to end the game.