I see this all the time with friends who pick up the guitar as a hobby. Often someone practices intensely for one week or one month and then gets frustrated at their progress. That frustration often causes people to give up. Now I see it as a mismatch between short-term estimation/expectations. The frustration is caused by overestimating how much progress they think they should make in the short-term. The quitting is caused by underestimating the progress they could make in the long term.