Thinking it through

I didn't workout tonight. I just didn't have the heart to do it. I feel like someone has come along and let all the air out of my motivation bag. I could blame it on my period this week, but I that doesn't seem really fair. Maybe I'm trying to do too much with P90X, running, and changing all my eating habits; and then I saw my measurements and I just don't know. Motivation has been zapped. It doesn't seem to matter how many motivational posters or quotes I read either...they're just pissing me off right now.
My sister gave me a book by Tosca Reno that I thought I would find inspirational and motivating. I'm interested in doing the eat clean "diet" but for some reason instead of inspiring me the book made me feel kind of sad. I really enjoy working out. I like the way it makes me feel both during and after the workouts, but I can honestly say that I never thought I'd be in my late 40's and 50's going to the gym and lifting weights or even still struggling with weight issues by that age. That's not how I see myself, or at least I didn't think it was. That is who Tosca Reno is. She didn't change her life until her 40's. That's when she started lifting and eating clean, and she's in the best shape of her life. She looks amazing, so it should be inspirational - right?!  So why am I so depressed about it?!
Maybe it's the way I was raised. My family just doesn't work out. My Dad worked hard in the fields all day and Mom worked hard chasing the 3 of us around all day. Healthy lifestyles just weren't apart of who we were, so I guess it makes sense that I never saw myself working out at a certain age. Maybe that's also why I'm so drawn to the fitness lifestyles.
I find my father-in-law inspirational. When his wife passed he turned his life around. He started eating healthier (even when everyone gave him crap about those shakes he was always making) and became very active with riding his bike, and he started going to the gym again (him and Chris used to do funny little challenges). It was amazing watching him transform his body.
How can people older then me (I'm only 34) find the motivation and drive to change their lives and yet I still struggle with it? I've always struggled with it...does that mean I always will??
I think fitness is important, and so does my husband. I know it will always be a part of our lives. I guess I just never truly thought about being older and still having to worry about the way I look. Or maybe as we get older we stop worrying about how we look at start thinking of it more as how do we live longer? I want to be around for my kids. I want to see them grow old and have their own children. But does all that really rely on my being able to do P90X yoga?!
I don't know, maybe it wasn't the book or the running or the P90X stuff, maybe I'm just in a sort of funk right now. I'm sure it has lots to do with Chris being deployed and being home alone with 2 little ones 24/7. I only get a few precious hours to myself at the end of the day when the kiddos go to bed, so choosing to "press play" every night can become very taxing.
I guess it's time to dig deep and figure out why I'm really doing all of this. Is it for my kids? Is it so that I can finally wear a pair of shorts and not feel like I'm grossing everyone out? Maybe I just need to think about what I really, truly want and my motivation will come back.