There was a very well thought out thread a couple weeks ago that explained in detail how and why your abilities are very dependent upon your level of health. Some folks like to skimp on food, saving it for their corpse runs I guess, but it's best to food up as much as you can for your biome level. You can test this at a GD spawner, in fact spending some time at a spawner is great practice, especially against the brutes. Also gives you lots of practice becoming fast on your feet, learning when to be defensive, back up, strafe, dodge roll, choosing different weapons. And at the lower levels it helps improve skill levels. It's like the skeles in the BCs, they are very good parry practice, especially if you can get 2 to 3 working in unison. It's a great place to see how the stagger meter works, how much parrying costs vs just holding up the shield. Better to know your weapons in a fairly controlled area than when you are facing a panic issue.
The other thing to look at is the color of your damage numbers. Using a great weapon an enemy is resistant to (gray numbers) isn't helpful, white better than gray, but seeing yellow numbers (weakness to that damage) is a wonderful thing.
Being old with slow reflexes, I depend a lot on muscle memory, just can't remember where I put it...