If I could give some advice to my past self, it would be to immediately start living on half of my income. That way, I could have paid off debt immediately and started saving.
I wasn't interested in finances back then, but great blogs have cropped up since, like Mr. Money Mustache.
It's about early retirement and I'm not so much interested in that. But after ten years of working for the Man, I wanted to start freelancing. Turns out that if you have a family, you want to have quite a bit of money stashed away when starting.
So I kept working in a job I lost interest in, just to save half a year of income. Only then could I make the step towards starting a business for myself.