With a job the things you have to do are usually pre-defined, you're being told what to do, you get a deadline and a guaranteed compensation.
It's like using a map that will get you where you want to go with as little roadblocks along the way as possible.
On the other hand, when you start a business or do projects you have exactly none of the above.
No pre-defined tasks.
No one tells you what to do.
You don't get any deadlines.
And there's no guaranteed compensation.
It's like you're in the middle of the jungle with no water, no food, no map and no clue where to go...