Accuracy over distance:
don't try to drive a fly, just get it in the right place. Let the rod load up then put it where it needs to go.

Impatients:
Too much casting and not enough fishn'! I once saw a couple on a boat just casting away never letting the fly settle long enough to get wet, like watching ping pong. (blew my mind).

Look:
Always check behind you as you fish, a snagged backcast is an ugly sight.

Line care:
CLEAN that line, use silicone cleaner/conditioner. Your line runs through the guides like poo through a goose (well, if I built the rod for you it does).