"individual affair" is correct and usable in written English.
For example, you could use it in a sentence such as, "This is an individual affair, so it's best to leave it to the person in question to decide."
Up in the West 80s it is a relatively informal, individual affair.
In her book Understanding Fashion, the cultural historian Elizabeth Rouse explains: "Clothing is not a random or totally individual affair: it is a social activity.
Thus, the social dimension of religion is a primary fact, but it need not be seen as opposed to religious experience taken as a wholly individual affair.
It's a significant choice of words, because it suggests a recognition that religious faith cannot be reduced to a purely private or individual affair.
Noteworthy, though, family members often pool money to remit and consider remittances a family, not merely an individual, affair (Eckstein, 2009: Chapter Six).
The single message of those who have realized such potential has always been the same, and basically, it comes down to this: True and lasting happiness and fulfillment are an individual affair and can only be found by going deep within, where one's true essence is vividly and stunningly revealed as love -- and then living into the reality of that awareness.
The sense of communal village living is fading: as in the big city, people are primarily concerned with their own individual affairs and those of their immediate family.
How concerned should the league be about what's currently on-going at Rangers? "It's very difficult for a league to get too concerned with the individual affairs of any one member club.
Since response to a moral rule is ultimately an individual or private affair, the notion of tiboa (conscience) is of great importance to our moral life.
DM often becomes a family issue instead of an individual's private affair.
It has been an oddly private affair, the individual tragedy of two people played out on a stage so small that it will admit no broader conclusions.
