I will first state I am not a trainer. This is my experience of going through similar, it feels horrible doing a bad landing, but don't worry, with time it will come to you.
I had an ex Boeing pilot tell me that the trick to landing an A320 is leaving the flare until you scare yourself. Tongue in cheek but true. Flaring too high always leads to a bad landing as you run out of energy and drop out of the sky or push the aircraft onto the runway.
My landing technique A320 series is check sensible ROD into the last 50' feet, don't dive towards the runway OR get shy of the ground! I only start the flare at 20' radalt. After you start the flare, smoothly reduce power to idle during the flare. 'Retard' is a reminder, not an instruction.
If you have a high ROD into the flare, flare a bit higher. If you have a strong headwind and low ROD or very light you might need to flare a bit later.
As well as flaring at the right height, the correct speed is important. Especially on the A321 make sure Vapp is at least 5 kts above the VLS on your PFD once configured.
I was initially taught 30' for the flare, I found it very hard to land. The chief pilot told me "Forget everything you have been taught. Flare at 20', bring thrust to idle at 10." From then on it clicked for me. Good luck.