I bought my first pair of "goal pants" years ago. I didn't meant to get them too small, I just didn't realize just how big I was yet and the store used a made up size system, so they appeared to be my size. I'd decided that I would fit into them one day, so I kept them. Trying them on was too disheartening for a very long time. But every time I could pull them further up than the last time, it was too exciting. I just put them on after a long time after reading this post and they are loose! It's a great feeling.
Other than that, because I bought all my clothes at M&S for years, every time I go down a pant size there, I buy a pair of pants that are one size smaller. I was a size 22 when I started, which is the biggest size they carry in my city and I'm getting close to wearing a size 8, which is the smaller size they carry here and has been my goal all along.
Lastly, the first pair of pants that I fit into that wasn't from M&S, was a size XXL and I did the same thing with those pants. I get one size smaller every time I go down a size. I'm almost a size S now!
So, I buy lots of goal pants. Ι love the feeling of being able to fit into them and it is very motivating. But I wouldn't like to have a pair of pants that I'll never fit into and I never hang them up where I can see them. I stash them away so they won't judge me when I'm eating nachos and cheese when I should be trying to make them fit.