Always best to soak them in hot water then shake it off as when you leave them out in the day they can alter slightly.
Keep the rubber mouth guard in a solution in the day with a bit of Milton in and soak in hot water before put it in .
Once you are use to wearing it I just left it in Milton in the day like you would do a baby bottle then rinse and pop it in.
My jaw was bad as a teenager and had to wear a day and night guard for years so got a good routine going....
You can also build up time wearing one also...lots of love glynis
Don't do what I did and ate spaghetti with it in and dyed it orange and would not come out...ops !!! Lots of love glynis