Leonardo was actually a bit lazy and known for not finishing what he started. He might have written that initial quote as an exhortation to himself 🙂 He was considered a great genius already at the time but also unreliable and messy (I.e. his Anghiari battle and his Last supper were a mess and started to get ruined right after he painted them).
But there is more to his personality, life, and art that hasn’t been fully revealed. I think I have solved the mystery of Mona Lisa and other of his paintings, check it out the photographic comparisons I propose should be enough to see that I have a very solid point, which finds plenty of confirmations in his biography and historical records.