I strongly believe that sims 3 is a superior game to 4. That being said, let me tell you a story.

Hypatia is a child, and like most children she looks forward to Halloween candy and Christmas presents. Luckily for her, both Spooky day and winterfest fall within her childhood.

Spooky day comes around and her mom throws a costume party. But where's the punch and candy that the notification told her to prepare? It doesn't exist. Okay, that only took me about half an hour to verify.
Hypatia changes into her little burglar costume and gleefully sets out to collect some candy. But nobody's home and those that are home lack the option to trick or trick. After spending what felt like decades of me researching how to do it properly, I still can't get her to go trick or treating, and it's the middle of the night. She's missed the party and didn't get any candy. Oh well I guess.
Christmas rolls around and Hypatia decides to throw a party herself. I get the house set up but no matter how much space I clear it won't spawn the gift pile. After a ton of research I finally download a buyable gift pile. It takes several reloads to show up, but finally! Party time! Only now routing errors make it impossible for them to open presents. Even when I get them all in the room, they leave it and go run around complaining they can't walk through walls. I consider demolishing a portion of my home (I've cleared the mandatory 6x6 of everything but the ceiling and windows) but end up dragging the present pile outside in the snow, where it finally works.
I've given up on the party, so it's just the 3 of them. Whatever. This is cozy. Mom calls them all to open presents and mom and dad sit down in the extremely large circle required. But hypatia is stuck and wanders off to play while mom and dad open presents without her. They get 7 fuducking chess tables.
FINE! Whatever. Hypatia has a recital today, so they head to that. I want them to hit the festival after, but the recital shouldn't take long, right?
Wrong.
They finally get to the festival, they might have just enough time for one family greeting card... they all make it in... an hour passes. 2. The festival shuts down. Mom walks out and pees herself. Hypatia comes out starving. Dad still hasn't come out. I'm forced to reset him.
They all go home and pass out on the front lawn.
Worst. Christmas. Ever.

I think we've all had multiple play sessions go like that. Our sims don't really care and it's not like the child will be scarred for life or anything, but I'm stubborn and will keep replaying them from a safe starting point until things go (closer to) the way they should. One wedding out of many in particular that I had arranged in a new wedding chapel I had just remodeled had so many things go wrong from the arrival of the first guests up through the cake cutting that I must have replayed it 15 times before I was satisfied. Since I got up to or through the exchange of vows on the majority of those reruns, that couple is really married now and they deserved no less.

I do the resetting thing, too, that's why it makes me so mad when I can't get it work! XD That is unacceptable! But if it weren't for things like that, lol, my sims lives would always be perfect tbh.

lol @igazor. Same here, I've got so many (forced) wedding celebrations messed up. Sometimes its that damn Llama Pox (from Nraas Vector) or those Sims stubbornly getting to work in the middle of the ceremony even though they are supposed to be married. Nobody stops a Sim from getting into their work, except fires, I guess.

I do forget every once in a while, but usually I manage to give the hosts and the important guests the day off by way of MasterController earlier in the day.

What I wasn't prepared for was the babysitter back home standing on the edge of the lot and then just stepping off of it, thus leaving the baby unattended and an important guest or a member of the to be wed couple being transported back home in the middle of everything. In the end, as of Round 12 or something, I got both the baby and the sitter to attend the party where I could keep an eye on both of them (not that the sitter was really on duty anymore). And what is it about wedding parties that makes everyone's bladder suddenly go weak? Since I didn't want to remove the lavish and comfortable rest room facilities but I didn't really want 80% of the guests choosing between getting stuck in there or peeing on the floor when they should have been happily dancing and mingling with the others, temporarily making that need static always becomes important as well.

I've never had a wedding where I didn't have to call my first attempt a 'rehearsal' and quit without saving. I've learned that it is best to move the bride or groom into the active household ahead of time so that I can be sure he/she will turn up, and won't get called away to work, or piss off to a pool party elsewhere in town. At my last attempt I built a special venue and, once the guests had arrived, I locked all the doors to prevent anybody from escaping. And, even though it was the week end and their day off, two of the family who were in Law Enforcement got summoned down to the precinct just before the ceremony.

@igazor: there are human's who always cry at weddings. Sims prefer to pee.

It's pretty funny, I've honestly not had any problems with weddings recently. I do move them in together if I'm going to have a ceremony. I don't usually have huge ceremonies, though.