Don't be. Pretty much everyone from age 18-25 or so is roughly in the same period of life, approaches things the same ways, and are interested in the same kinds of things. Also remember uni is not age segregated in the way school was, and you'll have people from all sorts of ages, different degree programmes, and even different cohorts ("year groups" in school parlance) in any given module, because everything is a real mix normally.
Also even mature students over the age of 25 can and do engage in all the usual trappings of uni student life if they so desire - it's just a bit less common because students of or above that age are sometimes less interested in doing so, often because they already have their own friends and family outside of uni and so uni for them is more of a professional endeavour and the other students their colleagues more than friends. But that is their choice, is the important point.