I did that in my truck on the way to work about a year ago. I was in the left turn lane and the light turned green. I for some reason thought it was a green arrow and jumped off the line! I realized my mistake and decided it was better to give more gas and get out of the way fast. But there was a teenager on a bike coming down the sidewalk, wanting to cross where I was trying to get out of the way. He had the "Walk" light, but thankfully saw what happened and waited for me.

I was shaking for the rest of the day!