Everyone has fears big and little. As adults we wisely shield children from adult worries, but sometimes we don't recognize a child's worries. Often it's the little things.
To feel confident and content one needs to have experience and realistic expectations. Children often have not had enough life experience to know all is well with some things adults think of as mundane.
It's important to be calm and positive and not belittle a child's fears. For example getting a first haircut from at a barber or salon can be very scary. A child is asked to sit in a large unfamiliar chair while a stranger with scissors stands behind them. For some children this is terrifying.
It's not difficult to change the situation from a scary confrontation to an exciting new adventure. Can your child watch while another family member gets a haircut first. Can your child choose a hair style. Many barbers let a young child sit in their parents lap for the first cut. Remember, the experience is more important than the actual haircut.
Some children fear going down the bath drain with the water and don't want to be in the tub when the water is drained. This is actually a fairly common fear. You can watch and show how the toys don't even fit down the drain. Make a game of watching the water swirl. You and your child can swirl the water more with your hands. Depending on your child you may talk about how the pipes take the water away. Follow your child's lead when a surprising fear is voiced and try to see it from your child's perspective. Be careful to answer the questions they actually ask and not go on with all you know about a subject - you don't want to accidentally add to your child's fears.
As adults we are often in a hurry or stressed. It's important to be calm and patient when helping a child through an unexpected fear.