Dreading this! :O
People doing this are also doing these things:
Entries
maybe silly but...
2 years ago
...it worked for me. Try to be conscious of when you say the letter “S.” Everytime you do, keep your teeth clenched and feel your tongue hit the back of your teeth and listen to the hissing sound it makes.
It’s probably better to do this on your own before practicing it in conversation. It’s awkward the moment you realize you’ve been hissing at someone for five minutes.

