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LULZ. Rembrandt is much more beautiful than that.
Ok, so, right off the bat: The eyes are too close together and too high on the face.
Looking at your reference: Your head is tilted to the left, the one in the painting is relatively straight. The nose needs to be bigger, and check the distance from the nose to the upper lip and the lower lip to the bottom of the chin - both are too long. The hat is also wider, particularly on the left. Watch that the shape of your jaw doesn't become too pointed.
I really struggle with master copies myself - I've got to do them over and over and over to even approach a semblance of accuracy. The best thing you can do is just keep at it.