I jumped straight from being a student to being a freelancer, so I didn't really experience 'normal' work hours until much later (as a contractor working on location).

I found that I did slowly gravitate to normal hours because of precisely this reason. My friends started having regular jobs and so I ended up having to adjust my working hours to that.

In fact, I was worse off because I didn't really realize I was conforming to normal work hours, but clients realized that they could approach me whenever they wanted, which was usually in the evening or the weekend.

It took me a while to learn how to not answer every email or phone call at odd times, and re-condition my clients.