The only regret I have from my honeymoon period is I started dating at 3 months which was a waste of time but it did not have a negative impact on my WL. It was just a bad choice overall. I wish I had started with DEXA scans and RMR testing earlier but honestly when I was in the 300s I would not have fit on the table. I barely fit when I started in the 200s. I feel like I knocked the food and tracking part out because it helped me change my relationship with food and it made post-op life easy mode.
As a super morbidly obese person, I did not need to add any lean mass. I already had more lean mass than most people (still do ) so my only concern was losing fat while keeping my lean mass, which I did by exceeding my Dr protein goals and keeping my protein at 90 or above from day 2. I am in the 120-130 grams of protein a day range right now. Working with a sports medicine team for my nutrition and fitness I think had yielded better results for me than following a WLS post-op plan, but that is a personal choice.
Oh I forgot at like 5 months I slowed my weight loss down on purpose because the month before I had lost like 20 pounds really fast, it happened all in like 10 days and it scared the hell out of me. That was a mistake, I should have just kept going the same way I was but, it was a lesson I needed to learn.
I don't think there is any losing too fast, it is better to let your body peel the weight off at the pace it wants. Your body is more in control than you are. It will take a break when it needs to, you don't have to build one.