There are three rules to making a good landing.
Unfortunately, nobody knows what they are.
Don't panic, and persevere. The art of landing is like riding a bicycle. You can't really be taught it. All an insturctor can do is to demonstrate, talk you through and (on occasion) help with a light hand on the flare. The rest is up to you, and sooner or later, like a kid learning to get "balance" on a bike, you'll get it. Thereafter, you'll never lose it again.
The main thing is to make sure you're set up for the approach in good time, trimmed, and stable with sensible power set - depending on conditions, around 15-1700 RPM will do it with two stages of flap and speed 65 kts. Thereafter, make only small corrections to attitude, heading or power, and make them early rather than having to make large corrections to get back on the GP or Rwy centreline or speed.
It's far, far easier to make a good landing from a good approach than it is off a poor approach. When nicely established, ensure checks are complete and get in your call "G-XXXX final". And then sit there, just making small corrections to keep the picture looking as it should. Don't react to the aircraft - instead, make IT do what YOU want.
Close the throttle all the way crossing the threshhold, marginally before you start the flare, and always remember the flare is not a single pull of the control column to check sink - it's a steady, almost continuous, slow rearward movement of the control column. If you run out of flying airspeed too high, just a small burst of power will slow the rate of sink.
Good luck!