I just finished my first 8 months of consulting work and while this is true, it is so difficult to actualize. When we had zero projects, I would take any meetings I could get. A part of me would hope that during the meeting, the client would realize where I could add value and increase their willingness to pay. In reality, however, it was the client who tried to push down our rate time after time. A hard lesson for a novice, but I lost hundreds of hours to clients that I knew, deep down, didn't have the budget.
With that being said, this is dangerous advice to internalize pre-maturely. Without underpricing yourself in the beginning, it's difficult to derive self-worth (IE: confidence) and increase your rate later on. And the last thing you want is an early freelancer to turn down work because they think they are worth more.
TLDR; Underpaid work might just be a rite of passage in freelancing. It was for me.