Competence makes you feel good.
The task can be fairly ordinary, like making coffee. If you are good at making coffee – gourmet coffee, that is – the simple act of brewing a great pot of coffee will make you feel good.
Conversely, if this isn’t something you do well, and your dinner guest are all coffee snobs, the act of making coffee will probably make you feel anxious.
It’s not much different if you are an employee at a company. If you are good at what you do, you will likely enjoy your work. But when a colleague takes a sick day, and you have to take on her tasks, which you are not so good at, that sense of satisfaction quickly evaporates.
All this is a preamble to suggesting that in your freelance life you should pay more attention to what you do best.