Time...

Definitely the most valuable and scarce resource. It's hard (with a 2.5 year old toddler and a 1.5 month old baby) to have enough time to:

• On DS: Play Exit, Picross and Etrian Odyssey
• On PS3: Play Ninja Gaiden Sigma
• On Wii: Play MadWorld and Punch-Out
• On Xbox 360: Play Silent Hill 5, Gears of War, Condemned 2, Dead Space on Hard mode
• Play Classical Guitar & Electric Guitar
• Play Piano
• Write an MP3 decoder/player from scratch
• Write an HLSL optimizer/extender from scratch
• Learn Scheme
  

But there will be time someday...