I am speaking from my own experience, but "pantsing" is less about writing willy-nilly and learning to trust your instincts. When I was a kid, I could never finish a story. I'd get too caught up in the planning stages that I'd lose all the enthusiasm I had for my great idea. It wasn't until I started to develop my own style that I finished stories.
I do want to make it clear that the ONLY difference between plotting and pantsing is the use of a formal outline. There are different styles of outlines that have different and distinct guidelines: Romancing the Story, Save the Cat, Hero's Journey, etc. Those outlines have goals for each chapter and beats that each chapter must hit. Writing down a list of characters and descriptions is not plotting. Making notes about random plot ideas you had while away from your computer is not plotting.
The biggest thing with pantsing or discovery writing is to trust your instincts: a character doesn't work - kill 'em/write them out of the story; you're tied of genre conventions/tropes - subvert them; the original ending you imagined for the MC doesn't work - start exploring new ones. If your instincts are telling you to try something with the story, do it. If it doesn't work, fix it in the next draft.