I think the greatest sign of immaturity is someone who jumps to a conclusion before knowing any facts (you'll get there one day). It's my biggest pet peeve and is as ignorant and immature as it gets. As far my limited knowledge goes, not meeting a workout goal, getting a flight bumped, and allegedly sleeping in isn't even signs of immaturity. That's life. Let's uh wait to see what happened?
And this might be a shocker tank, but just because people are similar ages doesn't mean anything, so comparisons are goofy.