Help a newly empty-nested plan a day of intense self-care in NYC! We're dropping our youngest off at college soon, and I'm preparing myself for an emotional upheaval of epic proportions. The following day, I'd like to spend a full day pampering myself—floating, massaging, art-ing, and generally rebuilding myself from the inside out. I've got the art part covered, but I'd love some recs for spas, floating in very warm water, and other glorious forms of spa pampering in NYC. Thank you!