With time and experience we change and everyday is a new learning process in our lives. So as human beings we change with time. There is hardly any person in this universe who doesn't change. Change can only stop when we stop breathing or die...
It is not that people want to change but it's the time and situations make a person so, sometime even in their is good news he can't be happy because of the situations he has passed, and when people meet that person they find him changed
People change due to the atmosphere,circumstances, situations, people around them, conditions, attitude and if they like any attitude then they change into that also
As said in hindi that "parivartan hi srishti ka niyam hai", so we all do come in that and thats why we all do change with the passing years and by having so many experience in life.
