one's long-cherished desire
武士としての本懐を遂げることができた。
He was able to fulfill his long-cherished desire as a samurai.
研究者としての本懐は真理の探究にある。
The long-cherished desire of a researcher lies in the pursuit of truth.
長年の本懐を果たし、彼は満足げに微笑んだ。
Having fulfilled his long-cherished wish, he smiled contentedly.