My hand is always heavy. I was in a car accident a few years ago and my strumming hand had to be surgically re-attached. I just try to focus/relax (if you know what I mean) and just play. I practice strumming patterns, but when it comes to playing songs, I don't think about a particular pattern. I try to come as close as I can to letting what is in my head go directly from my hand to my ears - and forget as much as I can about the guitar in the middle.
It's hard for me to explain, but I think about it as if it's my voice. If I want to adjust my voice, I respond to what I hear and make adjustments based on my ear. I don't consiously think about the mechanics of my voice (I'm not speaking to method singers) I just adjust on the fly.
Relax and don't be so mechanical. Try to google "guitar strumming" and find video clips of people strumming. I find it helps for me to see someone do it well and that allows me to better visualize what it should look/feel like.
Good Luck!
"There won't be any money. But when you die, on your death bed, you will receive total conciousness. So, I got that going for me. Which is nice." - Bill Murray, Caddyshack ~~ Michigan Music Dojo - http://michiganmusicdojo.com ~~