Speaking of Variety, vary your daily activities... don't spend TOO MUCH time on the guitar... I also play piano. I've been dating the same girl for over 2 years now. Playing pool is a big hobby of mine. I play sports - namely soccer, tennis, and basketball. Guitar is still a major daily activity, but it's something I look forward to rather than being like, well let me practice because I have nothing better to do... Take walks while thinking about music theory. The body and mind are intimately connected and stimulation of one is always always linked to stimulation of the other. Exercise. Take a break from the guitar anytime that it's not fun.

*** Oh yeah, and one big tip. If anyone around is better than you on your instrument, jam with them and watch and listen intently... The keyboard player at my church is awesome and I learn stuff every weekend just from listening.