I manifested a rabbit from a hat during a magic routine I once did as a kid...Oh, hang on, nah, that rabbit materialised due to the hours of effort I put into perfecting the magic trick and the false bottom in the hat...
I could try with all my might to manifest myself into an astronaut or world title MMA fighter...But that is never going to happen. Goals need to be realistic, measurable and have a time frame. If a goal is set in that way, and one focuses on the right things (activities and actions) then there is a chance the goal will be realised.
It seems to me that you understand the concept completely.
Now...I'm going to go an manifest a donut... :) (From the fridge)
True, limitations do apply.