For me, it's probably the mental game. I don't find myself losing it after a bad shot, and I've trained myself out of playing my opponents rather than the course for the most part.
My main weakness is max d. Since 400' is a rare occurrence for me at this point, there are just some holes that I'm not going to birdie. So I throw a fairway, and take my 3. The longer holes, like the 500'+ holes that almost nobody is going to 2 on the reg, those are fine for me because I'm accurate enough to get that 3 pretty easily. But holes in the 375'-450' range are the toughest because sometimes I'll have a look for 2, sometimes I won't.