This also just came to me recently in a discussion - The fact that an individual themselves can be their own obstacle in case they overshoot their goals, especially having in mind what they are capable of becoming or doing.
This is probably the biggest obstacle, being realistic about these things.
I agree. Sometimes people decline a good job offer only because they want "a business of their own". They don't want to work for another person or an organization, thinking that if they had their own business, they would be earning more while working less. This illusion is the biggest obstacle to achieving financial freedom for many people.