The one thing that helped me improve was when I stopped trying to crush my drives. I still use my driver but I just take a nice easy swing with it and try to hit the ball straight. I don't have a lot of length, but most of my drives end up in the fairway where I have a reasonable chance from there. When I get into trouble is when I try to hit it too hard and then I end up slicing it or just plain not making good solid contact.
I do agree that ego can really mess up your game. Here's a case in point. I do pretty well between 125 and 150 yards out. I have a hard time inside that distance, unless I'm chipping. It's that shot from 70-100 yards that I have a lot of trouble with for some reason. I'm either too long or too short, but if I'm anywhere between 125-150, I can usually put it on the green and not be too far away from the hole. Because of that I try to play my longer shots with a mind to give myself an approach shot somewhere in that range. If I get one of those short par 4 holes where a good drive might put me inside 100 yards, I like to hit a shorter club off the tee and give myself something over 100 yards. Maybe I need to work more on those shorter shots, but I've noticed that I shoot better scores when I sometimes hit a shorter drive and have an approach shot I'm more comfortable with.