Good job! When overlaying, it seems all your major landmarks were very accurate. The differences occur in the smaller details--the curvature and angles of the eyes, nose, and lips. It can help to use your pencil or a similar tool like a stick to measure out the angle on the reference and copy it down the page to use a guide. It can also help to periodically cross reference the placement of an area with a second landmark (e.g. if you placed the lip based on the eye placement, cross-reference with brow). It appears that the placement of the pupil + top of the eye was out of place, which affected the length of the lips, and in turn the width of the nose. Having a cross-reference, especially when you feel like something isn't quite right, will help catch deviations early on.

Fabulous. I think it may need a little more value transitions....what do you think? Some light is hitting the stem. Perhaps a little darker right where the pear is touching the table in the shadow. I'm no expert...