Replying to Consistent golfers

Golfers of Newschoolers, specifically you low handicappers (I know you're out there), how do you stay consistent? This is my first year back on the course playing seriously since high school where I was roughly a 6 handicap. Recently, I've been recording some of my best scores I've ever shot but along with some of the worst... and they usually are happening back to back if not in the same round. For example, last night I shot an 80: 34-46, it was as if I literally turned into a different player after the turn.

My question to you guys is how do you stay consistent throughout an entire round and what are some specific things you do mentally that keeps you in the zone? This has always been my downfall and it's something I need to address if I want to start competing again.

all answers are appreciated, even if you don't golf, how do you stay mentally sharp when it comes to athletics?