You can't. Therefore your excuses must be of the kind that few will want to discuss the next day, especially your boss. It won't do to suggest your mother-in-law has died, or that your cat has to be put down. People all want to offer sympathy about that sort of thing.
The classic "I must have eaten a bad shrimp" excuse might work once in a while, but overdo it and it calls into question your intestinal fortitude.
So here are five extreme excuses, to be used only in the highest of emergencies, when you need to break up your week without breaking your relationship with your employer.
This is a very fine one because no one will ask too much the next day. There you were, you say, taking your normal daily dose of, say, Xanax or some other mind-relaxant. Or least you thought it was your mind-relaxant. Instead, it was, say, your lover's super-strong fiber pills or a very, very organic diuretic. So there you are, feeling quite relaxed, but not entirely able to function at your optimum level. There might be a giggle at the other end of the phone. A guffaw, even. But it will be you who has the last laugh on the first tee.
Here's where you can truly confide in your boss. You can beg he or she to keep your secret quiet. You can, perhaps, not even reveal what your particular talent is. After all, there are so many talent shows these days that it could be singing, dancing, or tossing plates up in the air and catching them in your mouth. The most important part of this excuse is the shared confidence. You must explain that your chances are very thin. You must show the nerves of someone who is due on the first tee in a mere 45 minutes. Your boss, of all people, understands the pain of failure. She became a boss in order to avoid that pain. The next day, you can whisper, in a private moment, that it was the scariest thing you've ever done. A few weeks later, you can confide that you didn't make it. Your boss will have sympathy. Your boss will admire that you tried. Especially if you work for Avis.
The only sorts of allergies that are really worth anything are the allergies to the very simplest of things that very few people actually have. Too many people have allergies to nuts or pollen. Fewer are allergic to, say, ant stings. While 50% of people might, during their lives, be stung by fire ants, only 1% of those are susceptible to a severe reaction. This gives you a chance to get a little faux sympathy. Naturally, it will help if you confide in your boss that the sting has occurred in an embarrassing part of your body. This will prevent you from having to show signs of any pustules or bites. It will also reduce all conversation on the subject to an absolute minimum.
This might seem a little extreme, but it's a very good one if your boss is the sort that responds well to very personal confessions. This excuse works for men and women. Yes, it helps to be married with the more conservative bosses, but that is surely not an exclusive status these days. Importantly, no one will ask the next day, "How did it go?" And fortunately, especially if you are in cahoots with your spouse, this is an excuse that can be used more than once, without causing too much suspicion on the boss' part.
This is another one — when told in the correct, confidential manner — that can often pay dividends. If you describe something that has happened to you that everyone on earth prays never happens to them, you will likely elicit sympathy and very few questions the next day. Again, this excuse it personal, icky, and allows you to come to work the next day without having to do too much explaining. Might I add that, should the dreaded skunk-spraying ever happen to you, a mixture of soap, hydrogen peroxide and baking soda should do the trick.