If this is one of your unsuccessful efforts, could I please be your agent?
I rarely give much thought to "likeness" until quite late in the work, which will be long after I've put away the plumb lines or other tools I might find useful to get the parts of the "big look" in their correct orientation, in proper relation and proportion. There are few gumption traps as deep as having to erase or scrape off a "perfect" eye or mouth, or head or hand, because it was executed perfectly in an imperfect location.
One technique I use is to keep the artwork and the subject (whether live model or photo) close enough within my field of vision that I can pick out an area and rapidly look back and forth, back and forth, between the two. The mind's eye will hold both images long enough to register a comparison between them and tell you how they differ. This works (for me) for both shapes and values.
A couple of examples, using your drawing and the reference photo. Looking back and forth at the light area on the cheek on the viewer
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