I don't have a specific quote but what I do when I'm wavering is to take my goal as if I were hungry or thirsty, only until I satisfied I will stop.
“Light yourself on fire with passion and people will come from miles to watch you burn.†― Reverend John Wesley
''Life is a dream for the wise, a game for the fool, a comedy for the rich, a tragedy for the poor. '' -Sholom Aleichem