It's all in the mind...For something to be achieved it has to be thought of first. Or dreamed of first if you like! It is therefor not bad at all that you think you can become good at playing the piano.
Admittedly when you start playing the piano it is good to have an idea of how you see yourselves playing in a couple of years. Very often young students will have the idea 'Oh, no, but no classical music!'. I can understand that, because if the idea is only coming from the wishes of perhaps the parents then it will not always lead to good results. It can also work the other way around. My parents were somewhat shocked when I moved to classical music. That was soo not the thing to do. So my response will be to say that there is so much music that I surely am in a position to find the right music for my students and they have always choices.
But then the realisation. It is always a mystery for piano teachers why some students just fly off, where others take longer.
In the end of the day progress has to be thought of and it is a mind thing. Therefore I always try to find a challenging piece amongst other tasks which are easier. Those students who take any task and will work on it progress the fastest. They seem to enjoy any task hard or easy and don't think in terms of what other people might think of it, but what they themselves can make of it. For instance Paul was a student who only wanted to do a piece that was famous. But since he knew not so many piano pieces which were famous he was really limiting himself as to what he could do. He should realise that it is a person who at some stage picked up a piece and made the song famous, because of a good or new interpretation.
Then there are two other types of students. Those who think "oh, I could never do that" or those who are so fixated on the type of music they want to play that they are not open for all the good music which is out there.
There is only good and bad music.