Why we feel fear

Hello people, how are you guys I hope that everything is OK.

Yesterday I when we all my family to Split splash water rides, we have a great time specially my kids, they really enjoin the the kids swimming pool.

My son he's only two years old, and every time when he was swallowing water I pick he up and tell he that everything is OK, 15 seconds latter he was back in the water.

My daughter she's four years old and she also have a lovely time in the park, ok we all are having a great time , then I decide to my daughter and my wife to some of rides, we wore ridden like in four different rides, so I decide to keep walking and find a different ride, well we star make the line without know in what ride we going to get in, them few minutes later I realize that the ride where we going to it very tall, it was a big black pipe, in that moment I remember that my wife she is scare to the dark and my daughter star watching because she was getting nerves every time that we wore closing to get in the ride, so my daughter she star getting scare to them I talk to my wife if going to be like this our daughter going to be scare too, well the time to get in the until four person ride it came, now I was scare but not for the ride I was very scare that when we get into the big around dark pipe my daughter will be so scare and she maybe release from the big around flouting tube where we get into, any way we ride and guess what the ride it was very dark kind of scare but I star laugh when we wore riding, and when the ride was finish my daughter and my wife staring laugh whit me.

My question is why we had to feel this fear, even when we know that is only a game and not only this kind of fear I'm talking about all our fears.