If you fly the needles, it's natural to chase them. Try flying a Rate of Descent instead.
Method 1 - RoD = 5 x groundspeed (eg. 120kt g/s x 5 = 600 fpm)
Method 2 - (Same result) Add '0' to g/s then divide by 2 (eg 120 kts = 1200 / 2 = 600 fpm RoD)
If you get low, minimise your RoD (say to 100 - 200 fpm RoD) instead of chasing the needle up. As the needle comes back start to re-adopt ~600 fpm. The opposite applies if you get high.
The needles are
very sensitive. As
slim_slag said, make minimal control inputs and work really hard at holding heading. I used to literally cover the needles up and get students to fly an accurate RoD and heading. You would be surprised at how accurate it was.
Use a heading bug if it's available. If you're using a HSI - make sure that you set an accurate runway direction (to the nearest degree). Make sure you trim the aircraft to fly hands off. Set up and test the Markers / Locators well in advance (in or before the pattern). Most of all - R e l a x
