How to Stop Thumb Sucking?

My parents have been nagging me to stop sucking my thumb because they stopped smoking i always tell them its a little easier to quit smoking cause you can just not go buy them and with a thumb it's right there and it's not just to do it it comforts you and blah blah i'm tired of excuses i need to stop now i need braces and i'm so mad i cant get them until i stop my orthodontist put in a thumb inhibitor and i stopped for a year (1 month with out the mouth piece) but started up again a while later I have tried to just fight the urges but i end up doing it without realizing it (only lasts about 1 minute b4 i notice) My parents always say if we can stop smoking cold turkey you can do the same well i used to have nail polish that help stop nail biting and i just washed it off my mother put chili pepper and i accidentally rubbed my eye and she never did that again i try and try but i just can't do it! Please help whenever we try and talk about it i somehow end up in tears of embarrment I just want to stop and stop NOW i'm going into 7th grade and it has to stop. Please Help!