I was a nail biter at school and went through a paint them every night phase to cure myself of biting.
The thing I hate most in the world is chipped nail varnish though (close second is nails of differing lengths), so for years I had phase of nicely manicured and buffed nails, kept healthy with application of nail oil. Painted toes in summer as they don't chip as much. So yes, I think it makes a difference whether your nails look nice or not, but nice can just be neat and clean (bit of handcream never goes amiss).
But shellac has been revelation for me, especially with the brisa lite smoothing underlay. Finish lasts 2-3 weeks with care, doesn't chip, makes my nails break less often. it end not to go for nail art, but one of 4 pretty conservative things: plain red old hollywood manicure, a rouge noir type colour for nights out, a glittery red ruby slippers style for Xmas or gold for summer holidays.
Honestly, when I have shellac done, I smile every time I happen to inadvertantly catch sight of my fingertips. So it makes a difference to me, because it cheers me up. having it done is a real self-esteem thing too- taking an hour for yourself and spending a bit of money on yourself can make a big difference. When I've been really skint, doing the filing and buffing and moisturising has had the same effect, because I've taken the time to do something for me.