I found for myself that listening to my own playing is one of the most difficult things, if not the most difficult thing, yet it is absolutely crucial for the development of technique. Without the ability to listen, technical progress will be hampered, because, simply put, sound is the end-product of making music, and everything is judged by it. There are two issues:
1. One is so absorbed with pressing the right keys at the right time that one can't concentrate on listening. There are two approaches to this issue. One is to simply wait for the skills to be improved so much that listening becomes feasible. The next step is then being able to sing along with one's playing, and finally, to sing one voice while playing another. The other approach is recording one's own playing, as mentioned already. I always find this extremely sobering, because the human brain (mine anyway) has a certain sound in mind, but my fingers produce a different sound. Yet, my brain thinks the sound came out right, because it has a pre-conceived notion. This leads to the second issue.
2. Listening is difficult; generally, the perception of subtle differences of sound is a non-trivial task, even if one does not have a preconceived notion about the sound. I could initially not distinguish between a chord that sounded slightly harsh compared to it sounding smooth, mellow, etc. This is simply because the human ear needs to be trained as much as the fingers. If one can't distinguish between subtle shadings of tone color, one can also not produce them reliably and accurately. The solution to this is to make an effort to listen very carefully and to work out the relationship between the sound and the motions employed to produce it. For this type of "exercise", play only as fast as you can listen to your playing, because absolute concentration is vital. For best results, the piano must be tuned and regulated properly; do not watch TV while doing technical exercises (if you are doing them in the first place). Finally, incorporate eartraining in your lessons, such as identifying minor vs. major chords, how many notes have been pressed, harsh vs. mellow, etc.
Be patient
