There are too many things to learn;
I'm too old;
I'm never going to play/improvise/compose like (fill in the blank);
I'm not talented enough;
I don't have a good teacher;
I don't know where to start;
It turns out that if you focus on what you already know, it's all downhill from there.
I'm really good at playing this harmonic minor scale;
the first/last line of this piece comes very naturally to me;
I can play the left hand part fluently already;
This hymn gives me no trouble;
I completely nailed the pedal part of this piece;
I can play this chord in any key I want;
Look deeply at your skills, pick the best one and build on it.