There are 2 things that can be stressful when having parties. One is time. The other is money. Personally, I've found that time is usually the more prohibitive one. Therefore, I find as many ways possible to save time when it's party time. This weekend I did this in a few different ways. I baked margarita cupcakes (Muffin Tin Monday post coming soon) on Thursday and put them in the fridge. I made up the frosting, and put it in containers in the fridge. The only last minute thing I had to do was put the frosting on the cupcakes and put them in a pretty dish. They tasted fresh, and the frosting when on much more smoothly being cold.
The other thing I did was buy pre made items. The breakfast casserole from GFS was wonderful. Once it was cooked in the foil pan it came in, I scooped it out and served it in one of my pretty dishes. DO NOT feel guilty about serving pre made items rather than making them yourself. If you have determined that time is your normal party prohibitor, then using pre made items to be able to have a party is just the way you have to do it. So long as the food is good and everyone has a good time, then just accept it. Put your extra touches in how you present it. If people don't like it, then they can bring their own dishes. Parties are about having fun. Not about giving yourself a headache.
If cost is your main party prohibitor, then start planning your party a few weeks in advance. Holidays are generally good times to stock up on certain foods. I bought a ton of hot dogs a couple weeks ago because it was the cheapest I've seen them all season. A few packs in the fridge, the rest in the freezer. If I had wanted to, we could have easily grilled out hot dogs along with some other things to throw together a nice party on a small budget. Also, making home made dishes is generally cheaper than buying pre made ones.
Generally, I tend to combine the two. I opt for a few homemade things, and a few pre made ones. Any way you choose to do it, parties can be doable and less stressful with just a little bit of planning.