I am flying 737, but maybe I can offer some general pointers?
If you are having a bad stretch, the result may be that on every subsequent landing you are "trying too hard".
Unconsciously, you may be trying to take every input available in order to find that "magic tool" that will help to smooth things out. In doing so your attention may be divided between outside and instruments, and your eyes racing around looking at different places to take in all input. All in the most critical seconds before touchdown, where your eyes should be one place only - outside!
Forget everything you tried so far and start over. When it comes to landing, every aircraft is an aircraft, no matter what they wrote on the outside, and what boxes they put in the E&E compartment. Only the size and timing of your inputs may vary, but the technique is the same. Basically it's all about bringing the thrust to idle and the raising the nose and nothing else.
Some general tips, that works for all aircrafts, partly copied from another post of mine on landing the 737:
1)
Fix the runway aiming point markers in the window and only look in to check speed.
If you fly the ILS, eyes inside, down to last 100 feet and subsequently have to make larger variations to your sink rate when looking outside, it's difficult to get consistency in your landings.
Ideally your eyes should primarily be looking outside from the last 500 feet, or with suitable visual references latest, until touchdown. In good weather I would recommend from 500 feet (or even earlier when you see the aim-point) to gradually switch you path guidance from the ILS to fixing the aim-point, and from 300 feet on completely stop looking at the instruments, except to check speed.
The glideslope, PAPI and Touchdown markings are often not co-located, hence all this information may unstabilize the path at the last moment if switching focus between them in the expectation that it's possible to get them all to magically align. Actually they are all useless information, compared to the much more precise cues one can obtain from just fixating the aim-point in the window. Sticking to one cue, makes sure that the path and vertical speed remain the same.
Being where you want to be in a stabile state is the key to a greaser. If you were used to a very stabile aircraft you may not have had to work very hard on that in the past.
2) When reaching the recommended flare point for a 777, bring the thrust back to idle (altitude
pr. 777 FCTM). On the 737 a lot of people use a technique contrary to the recommendations in the FCTM (delayed thrust reduction) usually with poor results and longer landing than necessary.
3)
Switch view to end of runway. Don't look at the touchdown zone and don't let your eyes wonder inside to the instruments.
4) Use your vision to judge the vertical speed and adjust input as necessary. The perspective by looking at the far end of the runway, will give you the optimum premises for evaluating you vertical speed.
6) Use your feet to align the aircraft with the direction of travel. Even the lowest vertical speed will feel like a !!!!ty landing if you come down sideways (737NG is equally intolerant to drift). Compensation for loss of lift should now be easy, since you are already looking at the far end of the runway.
7)
Let it come down. Don't hold it off, like some previous posters already wrote.
Most "firm" arrivals are caused by not looking where you are supposed to… out the window!
Make sure you seat position is correct with regards to recommended eye reference position. Make sure you are not sitting too low. That will make it all easier.
My take is, that your mistake is being too much inside the cockpit. Being primarily outside already from the last 500 feet, takes out the surprises when reaching the flare point. And when reaching the flare point immediately switch all attention outside, bring the thrust back as recommended in your FCTM, and
and make sure that your eyes are looking/your undivided attention is at the far end of the runway.