This is very true. I think that a good taste is always ahead of one's works, almost by definition. I've never heard of an artist or a programmer who could just do exactly whatever they envisioned instead of a feeble attempt only.

(I bet Leonardo was never too happy with the smile of that little Mona Lisa either and probably couldn't really put his finger on what it was that he really wanted but couldn't just do.)

The counterpoint is that in order to live at least a relatively enjoyable life you will have to learn to cut yourself some slack. You have to have somebody, preferably yourself, to tell you that "This is enough effort; this is good enough for now and given your skills you've done well." Not that you could ever give up on your taste but I think that the acceptance of "I'm not good enough yet for what I want but that's okay because I haven't given up either" is what will eventually propel you to eventually accomplish even better works.