A warm, slightly old-fashioned command used downward, by a parent, teacher or older sibling: go and live your own life, drink, my dear sister, go out with your aunt first. It sounds affectionate rather than bossy, which is why it shows up in letters of advice and in the line telling someone to look after their health. Use it only toward someone clearly younger or lower in standing. One line here is a false match inside another word.
Register: affectionate and old-fashioned; strictly downward