As you practice more and more, you’ll get a feel for what the stitching behind the needle will look like. You’ll figure out how much movement makes the size loop, , line, or whatever. There’s no magic; it’s muscle memory that’s only developed with practice.
Every time I’m ready to FMQ, I practice on a sandwich about 20x20 to re-familiarize my hand-eye coordination, and to get relaxed.
Do you have quilting gloves? You can’t get a good grip on the fabric without them. I like Machingers.