Do things really happen in threes?

My grandma told me once that things in life happen in threes. Whether it's accidents, breakdowns, surprises, whatever they seem to happen in threes. This past week was no exception. You might call it a perfect trifecta of bad surprises.
Last Thursday I woke up made the perfunctory look in the mirror and was about to go on to brushing my teeth when something in my reflection caught my attention. The entire left side of my left eye was bright red. When I looked a little closer I noticed that it was also a little fuzzy feeling with some unpleasant goop in the corner. I had what I was pretty sure was pink eye. This is my first time to ever have pink eye, which is pretty amazing considering all the time I worked with children when I lived in America. the funny thing is that when I was little my grandma--not the one who told me all things happen in threes, the other one--told me you got pink eye from picking your nose and rubbing your eyes. So I spent my entire young life terrified of getting pink eye because I thought everyone would think I was a nose picker. Even when I went to the doctor Thursday I had to fight the urge to walk into the office and say "I swear I wasn't picking my nose and rubbing my eyes!". Thankfully it was a mild case and with a couple of doses of eyedrops it cleared up.
Then Sunday after church I was walking down the stairs from the church meeting room to the lobby. As usual my mind was somewhere in outerspace. All of the sudden I got sucked back to reality just in time to look down and think "Oh no, where's the next step??? Oh man, I'm totally about to fall down these steps!" And then...
Clunk, Thud, Thud, Snap..... Ouch.....
I somehow managed to end up in a sitting position on the second to last step, feeling incredibly stupid, as I usually do when I've done something super clumsy. There was thankfully no one else in the stairwell but there was a guy in the 3rd floor lobby waiting for the elevator who turned around to see what all the noise was coming down the steps. He looked at me and the irrational part of my brain just wanted to get out of there without looking any more ridiculous than I was already feeling so I just laughed and said "uh, hi." and stood up and kept walking down the stairs. From the fall I have a nice bruise on my lower back where I must have hit an edge of a step and a sore ankle/foot from twisting it as I fell. I actually heard it snap on the way down so I was really glad it wasn't broken, just a little swollen.
So Wednesday morning when I was leaving Taipei for south Taiwan on the high speed rail (which is really cool, but that's another blog) I was a little concerned because I'd had two things happen, but when would the third thing come?? I was hoping it wouldn't come in the form of a massive train derailment!
When I got off the train, after breathing a sigh of relief, I headed down to Kenting on the southern tip of the island with my Team Expansion co-workers, the Dunns (once again, another blog entry). I love going to Kenting because it's the best place to go to the ocean on the island. It's always beautiful there. This morning we went to the beach and there was a sign that said "Be careful of jellyfishes"--remember this is Taiwan. We were surprised because we didn't realize that Taiwan had jellyfish. I wasn't too worried about it because the water was so clear, I figured that you would be able to see anything before it got you. Silly, naive me...
About half an hour after I got in the water I felt this sting and tingling on my right leg. I looked down in the water and didn't see anything but then I felt the same thing on my left leg. It was so bizarre because it really hurt but i couldn't see what was stinging me! I thought maybe I was imagining it but I got out of the water and sure enough on my leg I had a couple of marks where I'd been stung by something. I guess if there had to be a third thing it could have been worse than being stung by a jellyfish, although it hurt like heck.
I don't consider myself a superstitious person, especially after living in Taiwan and seeing superstitions carried to a sad extreme. But I think it's just a little freaky how things really do seem to happen in threes. Does anyone have an explanation for why this happens? Or is it just that we think it's going to happen so we pay attention and see it? Please feel free to leave any opinions on this in the comments.
But one good thing about believing everything comes in threes--I shouldn't have any more painful experiences for a while. Hmm, maybe I have three good surprises coming my way!