Here’s one that’s SDMB related…
I stop myself from posting congrats and “stay sticky!” when Dopers announce they’re pregnant, because the first couple of times I did the Dopers lost their babies. Even though I know intellectually nothing I said caused this, I try to refrain until the Doper baby emerges safely.
Anyone else? SDMB or RL related.
My own weirdest – because I do not know why I do this! – is that I do not buy frozen food. I refuse even to walk down the frozen food aisle at the supermarket. I buy canned food…but never, ever, frozen. Not even so much as ice cream.
I’ve done this my entire adult life…and, sweartagod, I don’t have a damn clue why.
Now, I also say “…and a cat” when I’m totalling up sums, like when I’m buying stuff at the grocery. “Four dollars…and a cat. Seven fifty…and a cat. Twelve dollars…and a cat.” But I know why.
I have an add-a-puss complex.
I sometimes play 4-5-6 with friends. It’s a dice game wherein three dice are placed in a cup and the cup is slammed upside down on the table then removed to show the player’s roll. My superstitions are that I always flip my dollar bills Washington side up and always slam the cup on my money.
When I play roulette, my must-play numbers are 7, 8 and 15. I’m not into numerology, but I always liked that sum for some reason.
Beg pardon?
I’m not sure if this is superstition or lingering childhood trauma, but ever since I saw Psycho at a very young age, if I go to use the toilet and the shower curtain is closed, I take a peek to make sure there’s not a guy wearing his mom’s dress ready to stab me. This is probably one of my bigger secrets.
I started doing this the day that my boyfriend gave me a very tiny rubber Whale Shark to hang from my scooter. I touch it before and after each ride. I haven’t told him that I do this, although he may have noticed it. Also, when we scoot together - we pinky shake for a safe ride. If we forget to before we get on the road, we do so by the first traffic light or stop. I always feel better afterwards…especially on longer rides.
When I use my key fob to lock my car, I always do it twice. If I only do it once, I keep asking myself “Did I lock my car or not?” but if I double-lock it…yeah, that makes no sense.
I turn my back on the microwave so it doesn’t make my eyeballs boil. sadly, this is true.
I wouldn’t attend my son’s basketball games if they were on a winning streak. I would come up with an excuse.
If I’m driving behind someone that’s irritating me (too slow usually) that I can’t pass, but I know I’m turning off in a bit, I won’t hit my turn signal* until I’m sure they won’t also turn there. I don’t want to jinx them into turning onto the same road.
Oh, the list is very long…but I’ll list a few:
Left shoe on first. No exceptions. I WILL have a bad day if I deviate from this.
Awhile back (When the Mets were actually decent) If I watched the game on the Upstairs TV, they would lose, and I had to skip the first inning or again, they would lose. (Now they just plain lose no matter WHAT I do! 
)
I can’t drink my morning coffee/tea on my 50 mile commute until I am past a certain landmark.I WILL have a bad day if I deviate from this.
When I go skiing, I never announce to myself or anyone else with me that my last run of the day will be the last run. I always say “OK, two more runs, then we go in”, but actually only take one more run. Because you always hurt yourself on the last run of the day, and I want to cheat fate.
Yes, I know. I do it anyway.
“Stay sticky” is used to indicate a hope that a pregnancy will continue, that the embryo/fetus will “stick” inside the uterus.
When I had a horse I wouldn’t ride if I was wearing a white shirt. Never failed, if I was wearing white I’d get thrown and never get the mud/grass stains out.
My mother always told us that noise attracts lightening so we had to be quiet during thunder storms. She heard that from her grandmother who always had a houseful of kids, she probably made it up for her sanity. I still feel like I have to be quiet during storms.
That’s crazy, irrational, and just plain dumb.
I do it too, though.
Every morning, when I zoom over the highest point on the freeway system, I have to yell "Top of the world, Ma!" I actually enjoy it.
If we are crawling very slowly, I only mutter it.
I pick up all money I find, even pennies, because I don’t want the universe to think I have too much money and stop sending me some.
I try to go an entire month without buying gas. Not for lack of funds, not to “get back at” the oil companies, just because. 
The gas tank in my car holds just over 12 gallons, and I’ve more than once left the fill-up to the point where I bought 12 gallons of gas. :eek: Only once did I actually run the tank dry, and thankfully I was (1) able to pull into a parking space before the car stopped so I wasn’t stalled in the middle of the street, and (2) within walking distance of a gas station. Didn’t cure me of playing this little “game” though. :smack:
I’ve been known to do the same thing. Man, isn’t it going to suck when he just happens to be there one day.
I play the same two numbers in the lottery every draw. Been doing it for years. I have to, because if I don’t play THOSE NUMBERS one time, and one of them hits…it will be proof that there is a God and he hates me.