Believing I can lose weight and maintain it

I struggle with losing weight for several reasons, but I think one big reason is not really believing I can lose 80 lbs and keep it off (and the thought of regain is scary and I worry about embarrassment/shame about that)… I yo yo a lot, for example I have lost and gain 10 lbs several times this past year… I don’t even think I believe I can maintain the 10 lb loss (because it’s lower than I’ve been for decades). I feel like this fear and lack of belief might be sabotaging me… How do I believe I can do big things?