“I have not failed. I’ve just found 10,000 ways that won’t work.” Thomas A. Edison
At work, your boss may frown on mistakes, but that does not mean that in your personal life you should hold yourself back.
Human Beings are what the author and plastic surgeon Maxwell Maltz called servo mechanisms and what physician and educator Maria Montessori described as learning by constructivist or discovery model. We learn through experiential learning.
So if you wanted to develop a second income or take up a hobby, you must allow yourself to learn by trial and error. Just ask yourself what you plan to try and be prudent about it. The more you do it, the more confident you would be in yourself.