You make some really good points about needing to be a little selfish. I think of all the people in my life who need things a certain way, and how I go out of my way to accommodate. Oh, you go to bed really early, or you must eat dinner at 3pm, or you only like Italian food, or can't meet up at that time because you need to workout? Okay, I can be flexible! I'm turning 50 this coming year and it's only in the past few years I feel like I've started to learn to advocate for my own needs. And it's definitely a learning curve. It's so hard to remember that just because you could be flexible doesn't mean you always have to be.
As for relatives and food, my strongest childhood memory is probably my very obese grandma, who seemingly passed down 100% of her genes to me (thanks, Grandma!), saying within the span of two breaths: "You know, you're going to be overweight like me and you have to be so careful with what you eat...want more Polish sausage?" I mean, bless her heart, she lived to 92 and was sharp and reasonably active until the last year or two, so if she passed that gene along to me, I'll take it. But you can't tell a person one minute that they have to eat healthy and the next minute present them with an entire family-size Tupperware filled with grapes as a snack because "grapes are healthy." Which I would eat all of even if I didn't want them so as not to hurt her feelings. Meanwhile, my mom was rail thin and always going on some sort of "eat grapefruit for a week and melt the fat off" women's magazine fad diet my whole childhood.
Yikes. Family can do a number on you. And you're right, all that stuff will still be there to deal with emotionally even after the surgery...