Charles also spoke of the "ancient connections" and "modern friendship" between England and Ireland.
He said: "Our two countries are not just neighbours but partners who, though at times we have travelled a troubled road together, have through reconciliation and understanding forged a future that has benefited both our peoples and the world."
The couple had met with members of the local Ukrainian community and Charles also touched on the war-torn country in his speech.
He said: "I am sure your thoughts and prayers ... are with the people of Ukraine as they continue to face such uncertainty and brutal aggression. Such times as we are living through bring into sharp relief the importance of peace and friendship, which history tells us we can too easily take for granted."
Charles - whose father, Prince Philip, died last April aged 99 - encouraged people to celebrate those we have "loved and lost" with laughter as well as sorrow.
He insisted there is a need to "laugh as we always laughed" in the knowledge "nothing is past, nothing is lost".
He added: "This is true for all those of us who have lost loved ones in recent years. It is true for our countries and our people too."
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The Prince of Wales admitted hope is "badly needed" amid the coronavirus pandemic and praised the way people have come together.
He said: "Over the last two years we have all faced challenges which, before Covid, would have seemed unimaginable. Where once stood borders or seas dividing nations, we have been shown, in the starkest of terms, just how connected we are as a global community."
Closing his speech in Irish, he said: "Is deas a bheith arís le seanchairde."
The remark translated to: "It is good to be with old friends again."
