The 'ball hunting' mentality often kicks in when the ball is actually present. The swing becomes much too aggressive - shoulders take over, shaft gets way over the plane and becomes steep, the path may be overly out - to - in, etc.
It does indeed take a TON of discipline to trust the swing and not to pour on the MPH just because the ball is there. If the downswing is rushed, casting is likely the next thing to happen and it's possible to hit it thin or fat.
In order to shallow out the path, you can try a number of things. What sometimes works for me, is to stand up just a touch at address so the iron is barely touching the ground. Make a few practice swings and focus on just lightly brushing the turf. Try this a few times and then go ahead and really add some 'oomph' -- chances are you will hit it fat and/or take a divot that really plows into the ground.
When I want to work the ball from left to right or right to left, I focus on not trying to really hit down on the ball too much. I find that a 'skinny' divot results me being able to hit draws or fades. But I get too steep, all bets are off.