We overestimate our short-term ability, but underestimate our long-term ability
Tony Robbins has been saying this for decades. People overestimate what they can do in a year but massively underestimate what they can do in a decade. One implication being that if you take up a hobby (say, playing the piano) after a year you are probably not very good and a lot of people then give it up because their performance doesn’t meet their (over-)expectation. But stick with it, grinding it out year after year, and almost anyone can meet their expectations. The trick, of course, is to only undertake those few things which you think you’ll want to stick with over the long term.