how to stop biting your tongue

[lenguas]

i have been biting my tongue all my life, i do it when i am concentrated doing something, and i don't even notice until my jaw gets very tired. i have got a night mouth guard but it does not seems to do the trick, my jaw clicks a lot and it's very uncomfortable and i am worried that in a long term it causes bigger problems, can you tell me what can cause that and how can i stop it? every time i realise i am doing it i stop but it's hard to know when i can't even think about it.