A pentimento is an alteration in a painting, evidenced by traces of previous work, showing that the artist has changed his or her mind as to the composition during the process of painting.
A pentimento is the pivot of the art world.
It's the scribble in your notebook.
It's the backspace key.
Everything can always be improved so pentimental (I think I just made that word up) opportunities are all around us.
What can you find around you to improve?