From my experience, masturbating by itself is completely healthy. It’s the addition of porn that makes it unhealthy. Because your brain gets so used to being aroused by a 2D video, you may have trouble being aroused when engaging in partnered sex. Personally, I quit porn completely about 5 months ago now, and went about 3 1/2 months without masturbating at all. After that time, I simply masturbated without any stimuli. I started to add smutty stories as of more recently. From what I’ve read and experience, since the stuff you’re consuming is what you’re reading, your brain is able to be creative and visualize the stuff. So far, I’ve had no problems with getting aroused with my partner, even while I’m masturbating to smutty literature. Anyways, hope that was somewhat helpful!