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.
All my attempts are terrible compared to what I imagined, even if I'm trying to be practical. Some of my attempts work themselves out to be better or different than what I imagined. Its a crapshoot.
There are a lot of creative things I've quit on that I probably shouldn't have. I think in the end we need to embrace and be compassionate with inner noob. Sure, he's not good and he gets odd stares from non-creative people, but in the end he's the guy who blossoms into the guy who everyone dismisses as an "overnight success" or "natural talent." Everyone forgets how incredibly difficult and demoralizing it is to waste time producing sub-par work just for the off-chance that you might get good at something.
"...couldn't really put his finger on what it was that he really wanted but couldn't just do."
As an amusing literal interpretation of your metaphor, IIRC Leonardo actually painted the shadows around the Mona Lisa's mouth using his finger, which enabled his style of sfumato shading. So I suppose he was putting his finger on it...
(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.