I am finding this thread illuminating. I have never done anything to my nails as I have big square navvy hands with nails wider than they are long and I cannot bear the feel of my nails when they are longer than my figures, but I do love wearing rings, all of them reasonably clunky because even the most expensive tiny dainty one looks like something out of a Christmas cracker on my hands.
I am in absolute agreement with Mollygo, 'letting yourself go' has nothing to do with what clothes you wear or how you otherwise adorn yourself. It is a state of mind that expresses itself by making you neglectful and uncaring of yourself and it is expressed through body language as well as clothes and adornment.
Adornment is fun, it is present in almost every human species, going back to the beginning of time, and all of us do it - we all choose the clothes we wear and go on from there, whether it is make-up, or looking after your hands and painting your nails or getting out of bed and deciding, or not deciding what to wear.