non est ad astra mollis e terris via The road from earth to the stars is not easy. (Lucius Annaeus Seneca, a.k.a., Seneca the Younger).
longum iter est per praecepta, breve et efficax per exempla The journey by teaching is long, by examples - brief and effective. (Seneca the Younger)
errare est humanum. (Seneca the Younger - Roman Stoic philosopher, statesman and dramatist) To err is human.