from the research i've done, you basically have a "genetic reaction" to the surgery. in other words, don't beat yourself up or OBSESS (a big problem around here) about whether you lose 65% or 75% or 85% of your excess weight. the initial loss is virtually all out of your hands.
it's the long-term years afterwards that your behavior and healthy habits will determine if you keep it off. that's what you control. that's what you should focus on.
just try to be at peace with wherever you land after a year or so. it's nothing you did wrong (or right, tbh). it just is what it is. and it will be 1,000x better than where you were pre-surgery!