Why does it take so long to prepare for a vacation

I've been packing since last weekend, and I'm still feeling like I'm getting everything done at the last minute! Of course it doesn't help that I've been feeling sad this week because our cat, Isabelle, died Monday morning. She was a crabby old lady, at 15 years old, but it was still a surprise that she died so quickly. I'm glad that it didn't happen while we were in Alaska -- I would have been even more sad.