EEEEEK. Choosing my impossible goal!

I want to choose my impossible goal for next year, but I am unsure of what would be the best impossible goal for me.
I am in life coach certification and will be certified in March. I am a total beginner at being a life coach and I have never had my own business before—but I am excited about both and the journey I am embarking on. So, my question is: how big should I make my impossible goal? My very first thought was to make 100k this year as a life coach; it definitely feels (and seems) impossible. But, so does making 50k and even 25k at the moment. I guess I am worried about saying 100k because then I might go into ‘I gotta grind mode’ and that might happen with 50k too. When I think 25k, I think ‘okay, let me just take the steps and see where this leads me’. Am I playing it safe if I choose 25k? I want to challenge myself to do the impossible, but I also do not want to make it so huge that I give up.
I would love any clarity you can provide. I appreciate you taking the time to read and answer this.