If you could take your first trip again, what's the one piece of advice you wish you'd known?

Fear is heavy, knowledge is light. Only bring those things you need, not the things that might come in handy. Keep looking for gear that is lighter that what you have or what you are going to buy. Lightweight backpacking is the only way.

Is there one piece of gear you can't live without?

Well, it's more than one. Silk socks and Band-Aid blister pads (forget moleskin the blister pads are awesome) are up there.  I'd add my Gerber paraframe knife (very lightweight), Platypus gravity filter and JetBoil along with my Eno hammock or Big Agnes ultralight tent.  My "must have" luxury items are a mini down pillow, a Snow Peak double walled mug and my coffee (Kuju pour-over packets or Mocha Gold depending on how long the trip will be).

How can you physically and mentally get the most out of the experience? 

For me, a large part of the experience is the food.  I primarily do freezer-bag cooking so I know what goes into my meals and know that I'll enjoy them.  Don't forget the honey buns to have with coffee.

Deep down, what's the reason you keep getting out there?

To remind myself that I can.