More Experience, Less Planning?

It has been a long time since I've done an actual sewing project and not just a small something with needle and thread. And I don't think I've ever done a sewing project without someone with significantly more experience handy to give me advice and help.
That's why I'm out of practice.
But I tried my hand at sewing again and I made these covers for some hassocks that I'm recyling/making. The first one I cut out on one day and then spent 2 or 3 other days sewing it haphazardly, with a lot of unpicking. As a child I had a fierce aversion to pins, and I refused to use them in my sewing projects.... when I finally succeeded in some satisfactory corners this time around it was only because I finally sunk to such depths as to actually use pins. They were very helpful, and I think I only stuck myself once!
I realized a lot of things I go into a little haphazardly. As in I'll just chuck some shapes together in inkscape and they play around with them a bit and I just expect them to work out and look good enough.
Or I sketch something halfway and then play around with paint on top of it until I think it looks decent. But I don't generally plan out my projects in detail before I just kind of go for it. That is probably why I will never become a truly skilled artist. I don't want to put in the work.
But I'm usually fairly satisfied with the outcome, so it works.
However, sewing doesn't seem to work quite as well with this approach. I'm assuming that has more to do with my lack of experience and expertise then with sewing, because I'm pretty sure that is how my sister sews...
My second hassock I cut out, and pinned and sewed all in the same day without any unpicking... crazy what a little experience, and a little bit of slowing down can accomplish!