This is a very true quote, meaning that you should never give up, for the greatest thing in your life might be right around the corner. If you give in to temptation, you may never find out what success you could have had.
If diet is controlled, (food, sight, thoughts are diet for the mind) then mind will remain controlled. Mind is higher than the body and senses, and higher than the mind is the intellect. Body is only a chariot and mind is the main controller. Mind must be