In a chatroom long ago I had an argument with a 19-year-old who insisted that he'd never change his opinions. Gosh I wish I could find that guy again. Imagine a 33-year-old with the stagnant mind of a 19-year-old. His handle was "BOSS" so obviously he thought he knew everything.
At that time--14 years ago--I had no proof for my argument that his thinking would change, but since then there have been numerous studies done showing brain activity changes with maturity. I don't think we ever needed scientific proof that old age changes the brain--insert "mental-pause" joke here--but these studies showed there are significant differences between teen and adult brain activity. When you couple this fact with the experience you have to draw on as you get older, it'd be more difficult not to think differently.
I'm not saying that the changes will be drastic and immediately noticeable, since they happen over years and our attitudes are shaped by our culture, upbringing, friends, experiences, etc. A son of a Nazi growing up along other Nazis is probably not going to suddenly become a flower child once he's 30, unfortunately, but still he won't have the same opinion on everything. Maybe he'll decide chocolate is his new favorite flavor instead of vanilla, who knows? There's hope, however, that by age 50 he'll have life experiences that will change his attitude.
Up until my early thirties things were pretty much black and white to me, too, although I wouldn't have gone so far as to declare that my opinions would never change. I look back now and shake my head remembering judgments and decisions I made. Making decisions seemed much easier in those days. As I gained experience and knowledge over the years, all the different angles and outcomes have to be considered before I can make a decision. Young people just "do it" without considering every consequence and they have the energy to carry out their often risky plans.
Perhaps that is how it's meant to be and how mankind progresses. The world probably would be a much different place if people were born with the wisdom and better judgment of the elders: "Are you kidding, I'm not going to join Caesar's army and risk dying or coming home a paraplegic!" or "No Orville, I'm not getting into that flying contraption!"
So while there are a lot of bad decisions being made in our youth (deciding to smoke, trying meth "just once," letting a guy--or girl!--talk you into unprotected sex), thank goodness for that stage in life when we don't know enough not to attempt the impossible dream. So keep trying the impossible, but beware of the possible.
And if you're 19 and don't believe me, please save this in your personal time capsule to open when you're 59. I dare you!