So I was in the exact same boat as you. I had never really felt full and exams of that I ate ENORMOUS portions. I would have to eat like thanksgiving style I even feel satisfied. Yes, head hunger is a real thing but for the first time your body lets you know when you are full. Like truly, no shit, do not eat anymore. I was not perfect through this process and more than once I pushed it and spent the next 30 minutes laying on the floor waiting for the feeling to pass, and let me tell you, it certainly taught me not to do that again (or avoid what I did).
You hear this a lot on these forums, but honestly the sleeve is only a tool, it does not work miracles. You have to measure and TRACK (I use myfitnesspal every single day - no excuse - if I ate it, it gets recorded - to include the too many glasses of wine night or too many Christmas cookies).
It is scary and of course you'll go through moments of doubt, but once you start seeing even small victories - mine was being able to shop in a normal store, wearing a 14 again, getting past a previous weight hurdle (215), etc, - it is SUPER motivating.
Best thing I've EVER done for myself good luck to you!!