Ichi-go ichi-e
一期一会 describes a cultural concept of treasuring the unrepeatable nature of a moment. The term has been translated as "for this time only", and "once in a lifetime".
The term reminds people to cherish any gathering that they may take part in, citing the fact that any moment in life cannot be repeated; even when the same group of people get together in the same place again, a particular gathering will never be replicated.
Each moment is always a once-in-a-lifetime experience.