Impossible goal is starting to seem possible

I’ve set an impossible goal for 2021.  I’ve also spent December working on a belief which relates to my goal.  The belief is starting to feel true, but now my impossible goal doesn’t feel that impossible any more, rather it feels like it will happen as long as I don’t quit.  Should I make my goal bigger, work on my beliefs about quitting (for example, start to believe that I am someone who doesn’t quit), keep going with the goal I’ve got, or something else?