What is maturity?

I have never been sure about the words maturity and growing up in terms of a person's behaviour. There are times when these terms appear to be inherently subjective interpretations, where behaviour conforming to the observers expectation is considered mature and anything contrary to it is considered childish/immature. Is it really that simple? And perhaps more important than a 3rd person perspective, how do we evaluate our own maturity?

Back in high school days, I used to drive a two wheeler. I had once given a lift to a friend who was riding pillion behind me for the first time. He remarked as soon as we started that the jerk as we put the vehicle in motion was more than expected, and wondered if it was a case of the bike being more powerful than it looked or a simple driver error throttling too much too soon. I had replied without blinking an eyelid that the bike was powerful :P!

Fast forward to the present day. I had given a lift to a colleague in my car. We got stuck in a traffic jam going uphill and could feel occasional jerks in the car as it crawled up. My colleague remarked that perhaps my car needs servicing as the vibrations were noticeable. And what was my instant response this time? "The jerks are because of my bad driving and not the car. I tend to release the clutch a little too late when driving uphill in stop and start traffic, in the fear of stalling the car if I release too early. Perhaps this results in the gears not being completely engaged at times, resulting in the jerky movement for a second or two."

Is this a sign of maturity?

-Phani