Artists seem to worry a lot about things like what to paint, is it ok to paint from photos, is it plein air if I do it in the car, is it ok to paint pets, etc. A lot of energy is spent thinking about painting rather than actually painting. My advice to my students is to paint every chance you get! Doesn’t matter what or where, just paint (or draw). The more you do it, the better you will get.
My preference is to work from life or direct observation–but that is not always possible. I may not have access to a model, or I may want to paint something it is not logistically possible to paint (the inside of the Holland Tunnel for example). Rather than agonizing over whether it is “OK” to paint it or not, I just do it. I always note my sources when I post my sketches online and use only my own reference materials.
Another thing that seems to create much consternation is the definition of plein air. Plein air means you painted something that is outside while you were outside. So is it ok to paint in your car? Of course, just say “I painted this from my car” when you post it or exhibit it. Edward Hopper painted from his car frequently, if the car is ok for him, it’s certainly ok for me. If the idea of not adhering to the strictest of definitions prevents you from painting, or from enjoying the process of painting, is it really worth it? I’d much rather paint inside my car on a cold rainy day than out in the elements, so I do.
The point is, get out there or stay in your studio, but whatever you do, get the paints out and paint. Or get the charcoal out and draw. The only way to improve is to do it every chance you get…in the manner that works best for you at the time!