保重 (bǎo zhòng) is the standard, polite phrase for 'take good care of yourself' when parting, focusing on health and well-being. 珍重 (zhēn zhòng) is more formal and also used when parting, but it emphasizes treasuring the relationship. Other siblings like 当心 (dāng xīn) and 留神 (liú shén) mean 'be careful' in the sense of watching for danger, not general self-care.