I used to pack everything that I though I might possibly need.
After a few trips checking and then dragging around an almost 50lb bag, I realized that I could do without more than half of the stuff I had packed.

I pack pretty light now. If it's domestic and for 5 days or less, and I am not bringing any tools, I don't check a bag. I know that since most of my trips are to medium or larger towns or cities, I can get anything that I really need once there.

Mych