When l was little I had a lisp, or was told I had one and people thought it was cute. So I thought I was cute and kept lisping. But when I was getting to be 12 or 11, the girls in my class said I acted childish with that"awful lisp". So that was when I talked to my parents and went to see a speech therapist.
So what is a lisp?
For some reason, my tongue was out of my mouth, instead of in, when I said the /s/ sound. It could also include the /z/ sound. And sometimes I would spit when I was talking, which was awful when you were getting to be a teenager.
Fortunately I had my front teeth and the speech therapist told me I had to keep my tongue in my mouth. To think of the front teeth as the door to a house
and the tongue belonged inside the house, in my mouth.
It was not hard time change this habit because I really wanted to. When I was older I learned that a lisp can be caused by a child having sinus problems causing the nasal passages to be clogged and the child breathes through their mouth. So the tongue, noticing that the door is open, is out of the mouth.