Life is the only art that we are required to practice without preparation, and without being allowed the preliminary trials, the failures and botches, that are essential for training.

This quote means that life is the only thing we have to do without any preparation, and without being able to make mistakes and try again. We don’t get the practice or the chances to make mistakes along the way that are common with any other form of art. Life is something that can’t be taken lightly and must be taken seriously.