As you get closer to the runway, the sensitivity of the CDI increases. Think of it as a funnel and you are getting towards the narrow bottom. I agree with the previous poster, you are chasing the needles. Note the heading and vertical speed early on during the approach. Depending on your groundspeed, the descent rate will be somewhere around 500-600 fpm. Corrections within the confines of the heading bug (+\- 5 degrees). Learn how to "bracket" your corrections. Also reference the pitch attitude required when on G/S on the attitude indicator. Don't fixate! Scan, scan, scan! A technique I learned when flying the "6-pack" on final approach is biasing towards "attitude/heading/vsi" (triangle scan) and of course cross-check the other instruments. You will soon figure out what power setting and descent rate required to target for your airspeed while nailing the G/S. Keep at it, you will get it with experience...