In Kindergarten, my son and his classmates were encouraged to write all the time. They had prompts everyday and free writing on Fridays. I attribute these practices to his current love for writing...and maybe because he has a few of my genes :)
One day he was given a prompt about how he was feeling. He was really happy (excited is more like it) and drew a huge smiley face upside down. When he realized his mistake he drew arrows to correct it. It made me smile and realize that we can always turn that frown upside down.