The easiest way to build confidence in your abilities is to putt well. Every time you save a stroke, your confidence increases. Putting does take skill and practice, however it is the simplest part of the game to master. Anyone can be a great putter, it just takes practice. Unfortunately, most players don't practice this part of their game. Here is a simple drill to help you improve your putting.
For this practice drill you will need your putter and one ball. This is a simple, fast and fun exercise. In fact this drill is so fast I do this almost every time I go to a course, whether I'm playing or practicing. Go to a golf course or practice facility that has a practice green. On your first few trips try to find a hole location that is relatively flat. As your skills increase, you can look for more challenging hole positions. Since you will be hogging a hole, you might need to vary the times you go until you find a time that is not crowded.
Start by placing your ball one foot from the hole and at the low side of the hole, so that your first putt is uphill. Putt the ball into the hole from this spot. Aim for the back of the cup. I want you to be aggressive, no fear of missing. This is not one of those miss and start all over drills.
If you have a pre-putt routine, and I highly recommend you do, use it on each and every shot. This is a good opportunity to refine and define your pre-putt routine. Take time to read the green. If you miss a putt, finish putting from wherever your ball comes to rest. In other words putt out every ball as if you were playing a regular round of golf. Keep putting until your ball is in the cup.
Go back to the position you started from two feet below the hole. Stand at that position and face the hole. Imagine you are looking at a clock and the hole is the center that the minute and hour arms pivot. This is your one o'clock starting position. From here move to the two o'clock position, the position directly to your left, and step back a foot.
Your second position is at two o'clock and two feet from the hole. From here putt your ball into the hole. Again, read the green, perform your pre-putt routine and be aggressive with your putt. Keep proceeding until you have circled the clock 1-1/2 times. So your third position will be at three o'clock and three feet from the hole. Your fourth position will be at four o'clock and four feet from the hole.
The drill is over when you are at six o'clock and eighteen feet from the hole. At completion you have putted from eighteen different positions. Each position becoming progressively more difficult. You have just simulated an eighteen hole round of putts.
To track your progress keep track of how many putts you make. The goal is to take 36 or less strokes per practice drill. Remember, putt out every ball, even from two inches. Count every stroke. Be honest with yourself. Keep this up and you will see improvement in your putting. This will translate into lower scores. Which translates into higher confidence. Which again translates into even lower scores.