My advice for young students would be not to compare yourselves to different age groups of students. You're like apples and oranges. I've seen a lot of young students dive straight into grad programs and they are generally more driven and self work harder at school because they aren't committed to a spouse, family, whatever other obligations the older students tend to have. That being said, there is an air of ease that exists among older students, so, whatever you do, just don't try to be or fit in with your peers if you simply do not have commonalities. Learn to exist professionally and you'll be treated with respect by your cohort. It's how I became a manager of PhD candidates and teaching their lab skills when I was 22 and only had a BA. Most of them were in their thirties. They could tell I was young, but they didn't know how young. It'll all work out. Age is nothing but a number.