写“我错了”的英语作文时，可以按照以下步骤进行：

开头

可以简单描述事情的起因，例如：“One Saturday evening after buying something in a shop, mum and I walked along a path back home.”

描述错误行为

详细描述你所犯的错误，例如：“Then I found a lawn, beside the path. If walking across the lawn we would arrive home quickly. Thinking of this, I looked around. Seeing few people coming, I strode into the lawn.”

妈妈的反应

描述妈妈对你的错误行为的反应和教导，例如：“But I heard mum calling me back at once. I said to mum, 'We can quickly get home by crossing it,' pointing to the opposite. Mum seriously said, 'The lawn is used to beautify the surroundings. You should take good care of it. And can such tender grass bear your stepping？'”

反思和道歉

表达你对自己错误行为的反思和道歉，例如：“I realized my mistake and apologized to mum. I promised to be more careful in the future.”

结尾

总结并强调从错误中学到的教训，例如：“I learned a valuable lesson that day and promised to always listen to my mum and take care of the environment.”

I Am Wrong

One Saturday evening after buying something in a shop, mum and I walked along a path back home. Then I found a lawn, beside the path. If walking across the lawn we would arrive home quickly. Thinking of this, I looked around. Seeing few people coming, I strode into the lawn. But I heard mum calling me back at once. I said to mum, "We can quickly get home by crossing it," pointing to the opposite. Mum seriously said, "The lawn is used to beautify the surroundings. You should take good care of it. And can such tender grass bear your stepping？"

I realized my mistake and apologized to mum. I promised to be more careful in the future. I learned a valuable lesson that day and promised to always listen to my mum and take care of the environment.

通过以上步骤，你可以写出一个完整且表达清晰的“我错了”的英语作文。希望这个示例对你有所帮助!