What you have done will be treasured, it was painted with love.
Skin tones are challenging as you are not only trying to match the colors but matching them under different lightings, ambient, daylight etc. Sargent would spend a whole day with a subject only to come in the next and scrape it all out. That isn't all bad as it leaves some natural shadows and contours to work with, and eliminates an over-worked area if possible.
The tendency is to paint lines for wrinkles rather than applying the tones as the skin folds change from one plane to the next, it's a little bit of both.
I'd say well done for your first portrait