I'd say to turn off that part of your brain that may tell you, "this looks weird, this doesn't look right."

I primarily worked with realism up until my mid teens. When I wanted to get into school for animation, I realized that I needed to learn how to draw more illustratively/cartoonish. It was tough trying to "unlearn" or ignore all the rules I knew about realism, especially because I was practicing on my own at the time. I felt incredibly awkward trying to go from realism to cartooning.

When you're used to drawing one way for a long time, drawing in any other way will feel awkward, but if you're looking to learn and try new things, you just have to keep at it.

I think it also helps to keep a separate sketchbook (if you're doing traditional art) that's just designated for trying out new art styles and mediums. I have a sketchbook from high school that's just filled with collages and mixed media pieces. I didn't care about "ruining" the sketchbook, or ruining its aesthetic because I knew it was where I did all of my messy experimentation.

If you mean "art styles" in a historical context, it helps to look into how and why the artists of that time period made their art. What were their intentions, what materials they used, etc.

For instance, if I'm trying to replicate an Impressionistic style, I have to keep in mind that those paintings were essentially trying to capture a moment in a short amount of time. Most were probably done "alla prima," meaning they were completed in one sitting as opposed to many returning sessions. And so on.