When combined, `精神 (jīngshen)` means “spirit,” “vigor,” or “energy.” Therefore, adding `没 (méi)` in front literally means “to not have spirit,” which perfectly captures the feeling of being drained and uninspired.
The concept of `精神 (jīngshen)` is deeply rooted in Chinese culture, particularly in ideas from Traditional Chinese Medicine (TCM). It's not just an abstract mood but is seen as a tangible part of one's overall health and life force (`气 qì`). Having good `精神` is a sign of a healthy, balanced individual. In Western culture, we might say “I'm feeling down,” “I'm in a funk,” or “I'm just drained.” These are excellent parallels. However, `没精神` is subtly different. While the Western phrases often separate mental feelings (“down”) from physical ones (“drained”), `没精神` holistically combines them. It describes a single, unified state of low vitality, where the mind and body are both lacking their usual spark. Complaining of being `没精神` is a common and culturally acceptable way to express that you're not feeling 100%, whether the cause is illness, fatigue, or emotional distress.
`没精神` is an extremely common, everyday phrase used in informal conversation.
It is generally considered informal and is most appropriate for conversations with friends, family, and colleagues you know well.