I can, therefore I am.

To know oneself, one should assert oneself.

It's always too early to quit.

The wise does at once what the fool does at last.

If you're going through hell, keep going.

Be gentle to all and stern with yourself.

Quality is not an act, it is a habit.

Be thine own palace, or the world's thy jail.

Be kind whenever possible. It is always possible.