I carry that fear every day of my life. I carried it every time I've lost a significant amount of weight (30-40 lbs). Eventually my fears became reality...I've always gained the weight back, PLUS more.
HOWEVER ... by losing significant amounts of weight 6-7 times in my adult life, I have proven to myself that IT CAN BE DONE. I can do it! I've done it! I know what has caused me to revert back to old eating habits & stopped exercising in the past. My challenge to myself is to find a way to NOT do that (AGAIN!) Sounds simple, eh? Well, it is! But by no means is it EASY. I fight with myself every single day about what foods I KNOW are not "good for me" ....but they TASTE so heavenly! I fight with myself almost at every meal "wow, that was delicious! I want some more!!" ....And hey, I'm a physical kinda broad, but some days I just want to mellow out in front of the boobtube & be a lazy chica! UGH!
So I *fear* that I will never beat that fear. Even tho I'm not at goal on *this round of weight loss*, I still fear gaining back up to my highest weight (192). And even when I was at 128 about 12 years ago, I STILL had that fat feeling ("why can't I get down to 120????" etc) and feared each little pound that showed on the scale, even when it was clearly water weight fluctuation.
For me, the bottom line is I FEAR FAT. In all its forms. I don't think I'll ever NOT fear it. And maybe that fear is outlandish, & maybe it hinders me somehow... but maybe, just maybe, it's a healthy fear in its own way & that's what's kept me from being 250 lbs (or more).