Almost every hole requires you to make three different types of swing: 1. A power swing to propel the ball long distances; 2. A finesse swing to pitch or chip the ball onto the putting surface if you didn't hit the green on your approach; 3. A putting stroke to roll the ball into the hole.
You probably focus much of your warm-up and practice sessions on some form of your power swing. Occasionally you'll practice putting, but pay scant attention to your chipping and pitching shots. This occurs for two reasons: 1) You believe that if you improve your power swings you won't need your short game, and 2) most golf facilities don't have adequate short-game practice areas. It adds up to little improvement in your game and less in your scoring.
To solve this problem, first find a golf course with great long-game and short-game practice facilities, such as those pictured here (Atunyote Course, home of the PGA Tour's Turning Stone Resort Championship, October 2 - 5). Then, do as I recommend to all of my students, including Tour players: Divide your practice time (whatever it may be) into 3 equal segments and focus on, in order, your 1) short game, 2) putting, and 3) power game. Write me after a few months (firstname.lastname@example.org) and let me know if this practice structure hasn't made a difference in your scoring.