Back on the wagon... again...

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In good times and bad times, food has been the best and worst things about my life. I cook and my girlfriend is a GREAT COOK! We are BOTH using MFP to shed weight. We just joined a new gym... but, for some reason, she makes reasons for not going, and then I don't go either. That's NOT helping.
Once I begin to hit the gym hard and constantly, it's hard to stop me from going. Once I start a walking program, I miss it, IF I didn't get it done every day. I also do Tai Chi, and beginning Yoga moves (two replaced knees make it hard to get on the ground and up again). For my birthday, last year, my girlfriend bought me a boxing platform (heavy bag and speed bag). Simply put... I can't imagine needing anything else to work out on... so why aren't I exhausting myself doing it?
SO... IT'S TIME, to get serious and be a better me. To do that, I need to be consistent and insightful, in terms of starting over and adding more weight, more aerobic time, and more laps (in the pool)... but when? How do I keep the routine fresh?
I'd be interested in hearing from people who do SPIN, Zumba, Body Beast, train in boxing, or do Tai Chi/Chi Gong.
I have DVD's for Tai Chi (Dr. Lam, David Dorian Ross), Gaiam DVD's on Yoga, and Garripoli on Chi Gong.
MAYBE... what I'm trying to do is put the right program together, in terms of days and what to do. Certainly NOT the easiest thing to do.
Hope everyone is having a good day.