So the rational decision making part that considers the long term plans and consequences of your actions isn't ready until much later down the road of your life. Which makes perfect sense why people prey upon their immaturity. Things such as enlisting, studying, smoking, drinking, eating, exercising, working, courting, signing up for student loans at expensive colleges, and voting, are all decisions that young adults can make without fully understanding of the long term payouts will be. What a funny world we live in.
Does this mean that you are not responsible for all of your decisions as a young adult? Probably not, but you have a slightly stacked deck against you. Does this mean when you hit 25 that you magically make only the best decisions for the long term? Absolutely not, everyone makes terrible decisions at all points in their lives. Just be aware and mindful of your situations that you are in and take a moment to think, reflect, and decide which path you want to take next.