Biggest fuck up?

My career began by accident. I didn't plan what I was doing. I fixed it by changing what I was doing.

A little explanation: I am a fine artist and maker. It turns out there is not enough money in portrait painting, even though I am very good. 

However, the time it took to learn that gave me networking skills and the confidence that I could work on my own. I'm currently an early-stage prototyper; I can build things to demonstrate a proof of concept and use existing technologies to solve problems. Ultimately, I fixed not having one working career by developing another instead.

Lightbulb moment

All the time, I get them. But as far as my career goes, it was realising I could just tell people what I was good at.  Learning to market myself was hard. Learning that I could present people with the option of having a problem solved was way better. I can solve your problems. It's what I do.

Useful advice

If you're no good with people, read How To Win Friends And Influence People by Dale Carnegie. If you are good with people, read it anyhow. It's dated in style but pure gold in content.