Learn English – Is there English counterpart to Japanese proverb, 一期一会 , meaning “Cherish once -in -a-lifetime encounter”

I met a married couple of elderly American tourists to Japan who are both attorney at law in Connecticut a few days ago, and happened to have to introduce a Japanese proverb, “一期一会 – Ichigo ichie” in our conversation over the dinner.
The word is believed to have been invented by 千利休- Sennorikyu（1522－1591),
the great master of tea ceremony.

According to Wikipedia,

“一期一会” is derived from a tea ceremony terminology meaning 亭主- Teishu
(host) and 客-Kyaku (guests) must show as much sincerity and
hospitability as possible in serving and relishing tea at a tea party in
recognition of it’s being the once-in-a-lifetime encounter. It is the
phrase to admonish you that the very moment you are meeting each other
is the once-in-a-lifetime event. Such opportunity as happened “only here and
only now” may never visit to you again. You should make your best to
show your sincerity, friendship and hospitability to your guest(s) as
well as a host. It also means that although you may be able to meet
your friend often or someday, you must face and receive your friend
by telling to yourself that it could be the last time, and never again, whenever you
meet him / her.

I had a little difficulty to explain the meaning of “一期一会” to American friends, who showed great interest in the phrase.

Is there a counterpart phrase in English to “一期一会” to quote as an example, which might have helped me to explain the meaning of the proverb fully?

P.S.

I'd like to add that I recently received a mail from my friend, Carolyn W. Kone, attorneys at law who lives in New Haven, Connecticut on this matter:

"I don't think that there is an English equivalent to the Japanese proverb that you wrote about. The concept that you must treat a once in a lifetime encounter with sincerity, etc is somehow not the way most Americans think, I believe, although such encounters are often the subjects of romances in American movies."