You can't possibly
fully understand "Murphy's Law" until you have kids. The have a way of bringing it out in the universe in a powerful way.
For example....
1) The baby will wait until you're dressed to spit up on you.
2) Diaper explosions always happen in
cute outfits.
3) The day you forget baby wipes at home, you will definitely need them.
4) Kids will wake up bright and early on days when you can sleep in and sleep in on days where you really need to be somewhere early.
5) Kids will develop an allergy to naps when you have 1000 things to do.
6) If you get sick, you're whole family will instantaneously also get sick and require care.
7) If you and your hubby are trying to get "physical" your child will have a bad dream or need to go potty.
8) If you have a busy day planned, your kids will wake up grumpy.
9) Your kiddos will feel obstinate on days that you have PMS.
10) When you're exhausted it will take twice as long as normal to get your kids to bed.
11) Your kid who nearly never pees their pants will have an accident on a day in which you left their change of clothes at home.
12) You'll either loose your keys when you're running late or realize upon starting up your vehicle that you don't have enough gas to get where you're going.
13) When you are expecting an important phone call, the kiddos will have run off with your phone.
14) People will drop by for surprise visits on days where your house is a
disaster.
(this isn't my house, but it reminded me of mine, some days)
15) When your car is clean, only yourself and your family will see it, but if it's been... let's say... Neglected?... you will need to give someone a ride.
16) Your wee one is going to wait until it's silent in a very public place to either announce that they passed gas or they filled their diaper.
17) Your kids will always wait until people are looking to tug on your clothes, or lift up your skirts, and thus exposing you to onlookers.
19) When siblings are playing nicely is always when someone gets hurt and ruins the fun.
20) The one time you don't bring snacks in the car, the kids will spend the whole time begging for them.
21) The one time you don't make your kid go potty before you leave because either your forgot or they said they didn't have to... 5 min down the road they make you stop somewhere public to use the restroom...
22) If your child is going to develop car sickness it's going to be at the beginning of a road trip.
23) If your baby is going to decide not to nurse much during the day, it's going to be a day in public... without nursing pads....
24) If you venture to have an evening glass of wine after the baby (who is still nursing) is in bed, they will decide for the first time in months to not sleep through the night.
25) Whenever you want to show off your sweet one's antics, they never cooperate.
26) If you plan big birthdays, with all the trimmings, no one shows up... if you keep it very basic and have barely enough, everyone comes and brings 2 guests. :)
27) If you make a quick dash to the store in your sweats, your whole high school reunion will be waiting for you, but if you are dressed up and feelin' gorgeous it will be a ghost town.
28) Some days you can plan to take a nap as soon as the munchkins get to sleep... but when they do, your mind starts racing with all the things you should be doing, or could be doing now that they're sleeping, and you end up not being able to sleep.
29) If you use the worlds "always" or "never" regarding your kids they will "always" prove you wrong ;)
30) There is always an available babysitter (ie family friends etc) until you really need one.
<-Yes, I'm Breastfeeding in this picture! 
