You don't have a butler, you don't have a maid, you don't have a spouse, child, or other staff. You live alone, with no human shield. Therefore you may ban all stop-bys, or simply not come to a doorbell or unexpected phone call summons. It's fun to hear later how flustered someone became when your car was in the driveway and your knickers on the line and they knocked and rang and you never appeared.
On the other hand, you are perfectly entitled to respond in your pajamas and invite your unheralded guest into a messy kitchen with a look of friendly insolence on your face. It's their fault for knocking. Or answer the phone, "Spinster Poison House. How may I direct your call?"
You could also get very, very rich by eating a bland diet and investing wisely all the money other people spend making their life presentable. Then hire a staff.
Christmas is for Christians and families. Don't go to a Christmas Eve service at the Congregational Church with your mother who wishes you'd given her grandchildren and your brother who is unhappily single to sit among the multipliers in their jewel-tone velvet and tartan flinging themselves and their accoutrements about like self-satisfied jesters. You will just end up weeping and crampy and possibly drinking too much wine out of a box from the gas station because nothing else is open.
On Cooking for One
You can eat the same thing every day, à la Hetty Green. You can eat packaged foods. You can eat fast food (the quality is going up). Cooking for one, other than slow-cooker recipes for a week of leftovers, can be wasteful of time, energy, bandwidth, and, for fuck's sake, food. Look up online how many calories you need to eat for your target weight and get yourself a case of KIND bars and frozen Indian dinners. Science matters. So does online shopping.
Do not feel obligated to throw dinner parties just because you have nice appliances and money left over (or at least relative to those whose relatives force them to buy boxed cereals and orange juice) or just because you can theoretically take a week to clean up because that stack in the sink isn't bothering anyone else. I suggest, instead, that you be the one who can be relied on to bring the actually good bottle of wine, the rare chocolates, the state-of-the-art-gadget house gift that will ease a tad the life of the poor group-living dinner-party-throwing friend.