How I spend my money is my affair.

我如何用钱是我自己的事。

《牛津词典》

That is my affair, not yours.

那是我的事，不是你的。

youdao

My affair was retaliatory.

我的出轨不过是种报复。

youdao

"I have made my drawings with the greatest accuracy, and the most minute attention", he wrote."In an affair of so much consequence to the dignity of the United States,"

VOA: special.2010.01.27

There, I continued my affair with rice puddings, exploring variations like Spanish arroz con leche, Indian kheer and khao niao sang khaya a sticky rice and coconut custard that's popular in Thailand.

WSJ: Nostalgic for Nursery Pudding

My affair with Tony Canning lasted a few months.

NEWYORKER: Hand on the Shoulder

Baggage stowed, I rode the subway to the Gamla Stan stop, where the atmosphere was more in line with my old affair.

WSJ: Still Crazy for Him After All These Years