In my professional life, I'd like to say I'm mostly self-taught. But to be truthful, I didn't teach myself. Hardly anyone does, unless they are a contractor or self-employed. It was on-the-job training; that is, experiencing new challenges and learning on the fly and with the help and guidance of some incredible managers.
I was schooled in the fine arts and got my MFA in Painting. But then, after years of struggling to find teaching work at the college level and working day jobs, I started my own apparel company. I eventually closed my business and went to work for one of my competitors as a T-Shirt designer. This was at the dawn of the computer era, so I taught myself everything I could on my own time at home, and then put it to work at the office, doing apparel, catalogs, marketing collateral, etc.
Eventually I moved up and started managing people and quickly discovered that managing designers was a lot like teaching, except you made a lot more money and weren't out of work every 9 months. And I was good at it. I loved inspiring, developing and leading creative people. And I found I loved business.
I eventually landed at a Fortune 100 apparel company and after 11 years worked my way up from director to VP overseeing 4 departments and 65 people. I had an incredible mentor there who gave me a new challenge or a new department or a promotion just when I needed it. I learned the "business" of business: financial reporting, budgets, HR goal setting, assortment planning, building presentation decks, doing cost/benefit analysis. All the things that they don't tell you you'll have to do when you think you want to be a CD. I am good at it and unlike many creative types, I also like it.
After I left the apparel/retail industry I moved over to the agency-side as an Executive Creative Director, doing strategic design, branding and consumer packaged goods. I had an incredible mentor there as well. I was learning on the job. I could lead designers, but knew little about strategic design or design thinking when I started. I learned to pitch and win new business, manage client relationships, build processes. All on the job.
My career isn't typical. As Paul Pressler used to say at the Gap, "A great career looks more like a web than a ladder." You have to teach yourself whatever you can, when you can. Be open to learning from managers, mentors, co-workers and even vendors. Take new challenges on. Embark on a new career trajectory even though you may only have a vague idea of where it's going or what you're doing. You'll learn more. Learning is one of the great joys in life. It should never end.