You Don’t Fill Every Second With Friendship
In Your Twenties: Not only do you use friends to pass the time, but you also pack every available moment with social time and spend only a limited amount of time on your own, (you know, when no one else is available to hang out). In fact, the idea of doing "social" things alone in public may freak you out.

In Your Thirties: You actually look forward to time alone and make it a part of your routine. Sometimes you'd rather take your dog to the park on your own or grab a cup of coffee solo so you can process your week in silence.