If by "change" you're asking, "when did I stop underselling myself and getting in over my head" then I am not sure I could identify a single point in time where that happened. It's been an improvement on a continuum.
Those early years certainly felt painful but in retrospect provided valuable concrete experience in negotiating, marketing, and self-assessment. I learned how to figure out what others really wanted, how much they should be willing to pay to achieve their goals, and (probably most importantly) whether or not I could deliver. That period of time, when computers were exploding into small businesses, was a little magical when it came to freelance programming.
Now, ~40 years later, I find myself applying those learned skills at my current job every day. I got lucky.
My apologies if I misunderstood your question and blathered on about something else.
