For me, it is time in the house on my own. I do need a lot of solitary time, always have. Fine when DH was working full time, his work involved a lot of overseas travel so my life had a nice balance, but since he retired, even though he still does freelance consultancy, the balance has changed.
Yesterday he went off on a rare business trip to Germany, back tomorrow. I have a bad cold so I am just hunkering down in front of the fire, watching box sets back to back and drinking lemon and honey with no-one to think of except myself. I am enjoying it.