I was ... 25 or 26 ... can't remember exactly. And it was with my wife who I've been married to now for 15 years. I can't say that I had any changes in my thought processes or felt somehow more whole or something. It was just something special I was (and continue to) share with the woman I love. Part of that might because I was older when I had my first sexual experience though; I was more mature and not still in the thralls of puberty.