Life itself is full of changes and everyone and everything in it, changes alongside it. Humans cannot remain the same, they change as they grow and explore what life brings their way. Just like it's commonly said, "20 children cannot stay together for 20 years". Life forces will come along the way in many forms and separate them.
This gives my answer to the contest's topic, "why do people change as they grow"
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A child will start school in the nursery sector, under the guidance and directives of their parents, primary school, the same thing, and sometimes, the same thing plays during the secondary school section. But when it's time to get into the university, there'll be some changes, which will be visible to the parents and maybe not the course they wanted the child to study, is what they've seen the child shown interest in. Let's say this child continues and during the admission process into the university, the child is given another course, different from what the child and the parents intended. This is a big change already in the life and path of the child. The new course will completely lead the child to another direction of life, meet different people, pass through different strange Exams in school and in life. One thing is very possible, whenever this child visits home, there'll be some different signs of change noticed by the parents of the child.
So, life situations change us. It's a very natural effect. Where we find ourselves per time has a lot to do with changes that happen to us.
As we all know, the people who switch in religions don't just wake up to do that, something must have prompted them and that's the change we are talking about.