Why not make a few simple goals first, and then move on to bigger things once you've accomplished those smaller goals? That may help you a lot in terms of being "successful"

You can even break big goals up into a bunch of mini goals. Think of it like weight loss. (This is the best example I can think of...) If you're 400lbs and your goal is to get down to 150lbs, should you set one big goal and say "I want to get down to 150 lbs"? Sure, but wouldn't it be nicer to say "my first goal is to get down to 350, and my next goal is to get down to 300, and the goal after that is to get to 250" etc etc? Your main goal could be "lose 250 lbs", but your mini goals are losing 50 lbs.

The trick is to not bite off more than you can chew. Baby steps.

And really, a lot of the examples you gave involve people accomplishing huuuuge goals. Do you know if they had a bunch of mini goals along the way? I'm betting they did, especially in the anxiety lady's case because there are usually multiple triggers for anxiety, and so you have to tackle each trigger.

But remember, we shouldn't compare ourselves to others. What I consider a success may not be what you consider a success

If you accomplish your mini goals, you will feel as though you've accomplished something! Good luck