Haruki Murakami said this quote

There is one thing I can say for certain: the older a person gets, the lonelier he becomes. It's true for everyone. But maybe that isn't wrong. What I mean is, in a sense our lives are nothing more than a series of stages to help us get used to loneliness. That being the case, there's no reason to complain. And besides who would be complaint to anyway? (A Walk To Kobe, Granta 124: Travel)