Let no youth have any anxiety about the upshot of his education, whatever the line of it may be. If he keeps faithfully busy each hour of the working day, he may safely leave the final result to itself. He can, with perfect certainty, count on waking up some fine morning to find himself one of the competent ones of his generation, in whatever pursuit he may have singled out.
I found this in the book "How to Develop Self Confidence and Influence People by Public Speaking" by Dale Carnegie. The quote is found in William James' book "Bicycling"