Hang on to your youthful enthusiasms — you'll be able to use them better when you're older.
Nomentum
Nothing great was ever achieved without enthusiasm.
In the end, it's not the years in your life that count. It's the life in your years.
Old age, which is dreaded by all men, is to me the sweetest and most pleasant period of my life.
It is not the man who has too little who is poor, but the one who hankers after more.
Through hardship to the stars.
Men who have made these discoveries before us are not our masters, but our guides.