So, why should you care about the size of your carry-on bag? Well, for one thing, it can make a big difference in how much stress you experience during your travels. If you have a bag that's too big, you'll be worrying about whether it will fit on the plane, and whether you'll have to pay extra fees to check it. But if you have a bag that's just the right size, you can breathe easy and focus on more important things... like what in-flight movie you're going to watch.
Another reason to care about carry-on size is that it can affect how much stuff you can bring with you on the plane. If you have a large carry-on, you might be tempted to pack too much, which can lead to overwhelm and clutter. But if you have a smaller bag, you'll be forced to pack lightly and prioritize the things that are really important to you.