When Donghae was still in Middle school, He and a good friend of his got  a job. And their job was to deliver milk and newspaper. They worked there for 6 months. His friend's family was that well off, so both of them worked hard together. In the end, after all the hard work, because he gave it all to his friend, he didn't earn any money. Donghae understood that his friend was in a more difficult position than he was in.