I remember insisting very strongly to teachers and friends that my body was just simply not cut out to play barre chords on a guitar. I was convinced that it was impossible. Turns out... it's not.
With music the contrast between the desired outcome and the actual results for a beginner is extremely, painfully, embarrassingly obvious. The whole point is that you want to make beautiful sounds, not horrible sounds. You want to be in tune, in rhythm, melodious, but instead you feel clumsy, weak, confused, tone deaf, and awkward.
So that can easily kill your whole motivation if you don't really internalize the idea of progressive learning.
John Holt's book "How Children Learn" has some thoughts about learning instruments.
> There is a special sense in which it may be fair to say that the child scientist is a less efficient thinker than the adult scientist. He is not as good at cutting out unnecessary and useless information, at simplifying the problem, at figuring out how to ask questions whose answers will give him the most information. Thus, a trained adult thinker, seeing a cello for the first time, would probably do in a few seconds what it takes a child much longer to do—bow each of the strings, to see what sounds they give, and then see what effect holding down a string with the left hand has on the sound made by that string
> That is, if—and it is a very big if—he could bring himself to touch the cello at all. Where the young child, at least until his thinking has been spoiled by adults, has a great advantage is in situations—and many, even most real life situations are like this—where there is so much seemingly senseless data that it is impossible to tell what questions to ask. He is much better at taking in this kind of data; he is better able to tolerate its confusion; and he is much better at picking out the patterns, hearing the faint signal amid all the noise. Above all, he is much less likely than adults to make hard and fast conclusions on the basis of too little data, or having made such conclusions, to refuse to consider any new data that does not support them. And these are the vital skills of thought which, in our hurry to get him thinking the way we do, we may very well stunt or destroy in the process of "educating him".
> But the greatest difference between children and adults is that most of the children to whom I offer a turn on the cello accept it, while most adults, particularly if they have never played any other instrument, refuse it.
One thing that really sparked my motivation for music even while I was sucking horribly was the realization that you can make pretty neat melodies in very simple ways, for example by just improvising on the 0 2 3 5 7 9 10 frets on the high E string and sometimes hitting the low E string for bass—this way you can sound kind of like an Indian raga without too much practice.