never practice mistakes .. !
I taught myself piano and guitar via lesson books, which I would just blaze through. Unfortunately although I learned how to play both instruments, I taught myself a lot of incorrect fingers and other habits that had to be unlearned. My fingering on an open D guitar chord still baffles many professionals! I tend to learn something I'm interested in really fast. I'm like a dog addicted to a ball in that I will rehearse it over and over and over. Fortunately I live alone and use headphones, so there's nobody to complain at three in the morning. I say that to say I understand the drive to learn by yourself. What I would recommend while your just learning is to proceed at a pace makes you happy, but find a way to touch base with an instructor once a month or so. Explain to them that you are concerned about technique and spend a half hour or an hour and see if you need to adjust your playing. As with most instruments it matter most on transitional issues. But fix it before it becomes a habit.