You lose your balance in your follow-through and frequently hit pushes and slices.
If you can groove a good finishing position first, it'll be easier to make the swing moves necessary to finish in balance and eliminate poor ball flight.
Use this Drill
1. Put on a baseball cap and take your normal address position with an iron.
2. Without moving your feet, stand straight up and bring your club straight up over the top of your head.
3. Make a quarter turn to the left with your face, chest and hips pointing at the target and the butt end of the club pointing to your left. This motion should naturally bring your right foot up onto its toe. You'll know you're in the ideal finishing position when you feel the shaft lay across the hair on the back of your head where it pokes out from the cap. Practice this drill and your swing will improve as your muscle memory naturally steers your body to a balanced finish.