Change is just fun if stuff didn't change the singulatity wouldn't have expanded into the universe in the big bang and I wouldn't have got a new hair cut.
Even though Estel stole my answer(darn kids these days), I am going to elaborate on it. XD
If creatures did not change/learn over the course of their lifetimes, they would die off. Nothing in this world is exactly static. Take, for example, a typical person. Assume that the person in question never advanced beyond the mentality of a preschooler. They would be, well, screwed.
Overall, change is just the brain rerouting paths and adapting behaviours and actions based off of past experiences.
Devoidless hit it right on the head. Without change we would become inept. Humans must evolve to stay ahead of nature. When Jesus was on Earth, the average fully grown male was around 4'8", we have slowly adapted to nature, learning, getting stronger, etc so that we can survive. It follows Darwins law of evolution "survival of the fittest"
I'm not a kid 'voidy! :P Well, maybe I act like one sometimes
Now answering the thread intro question: Changing like what I think is going on, is completely normal. It's not that you are "adapting," just changing because of your surroundings. A technical adaptation would take years to occur, but you get my point. It goes back to when you mature. Seeing new people does have an effect on you. Many of my old friends in VA have told me that I have changed. It's only been 6 months, but I have changed because of the people around me, mainly my girlfriend. Just being with her really does change the way I think on things and how I treat people.
