Impossible goal

I understand the concept of choosing an impossible goal when it comes to business, and I can think of a lot of potential impossible goals that I could choose for my business. What I really want to do in the year 2021, however, is get to my goal weight. I’m having a hard time seeing how that works as an impossible goal, though, because it is completely possible. I’m 5″4 and weigh 165 and haven’t weighed less than 150 lbs in over 25 years (I have never been a healthy weight for more than 6 months ever in my life. I think I was fat even as a toddler!) I can see myself reaching a healthy weight, even though currently I have no idea what that number is (I may choose a body fat percentage as an end point instead of a number on the scale.) Can I have a possible goal for an impossible goal?

Also, with weight loss, how do I fail 25 times a quarter? Do I set up mini goals within my goal? For example, do I say “I’m not going to eat any sugar this quarter”, then if I eat sugar it’s a failure? It sounds like a great opportunity to work on “all or nothing” mentality, but I’m not sure I’m taking the right approach.

All I know for sure, is reaching a healthy weight for the first time in my life is a goal I really want to achieve! Thank you!