A man who was seen chiseling a rock into a beautiful horse was asked, "How do you make a sculpture of a horse?" The artist responded, "I simply chisel away everything that doesn't look like a horse."Supposedly, Michelangelo himself put it this way:
|Michelangelo's Pietà (1498-99)|
So, the ideal performance of whatever piece you're practicing is the "angel" that you need to set free from the block of stone. The most important step is "seeing the angel." You need to have a crystal clear plan of how you want that music to sound, so that when you start "chiseling," you know what belongs and what doesn't.
Get rid of all the unnecessary stuff: extra tension, extra noise between the notes (slurs and articulations), awkward phrasing, etc.
Further, get out of your own way. Make it easier and more efficient.
The composer Adrian Ellis writes about these same concepts here. My favorite quote from his blog:
"The sculptor doesn’t look at the unformed stone as a hindrance! It’s simply the work that has to be done."