How do you know when you should be easier on yourself and when you need to light a fire under your ass regarding Zen?

As some may suspect, I suck at pretty much ANYTHING that requires that I be somewhere at a certain time. Even when I sat zazen everyday, I never did it at the same time. I can lift weights everyday for two weeks, but if I sign up for any sort of exercise class (Krav Maga, etc...), I just don't go. My job is pretty much the only place I show up at a certain time without at least a LITTLE bit of wiggle room about the when.

I'm thirty-four and I've misguidedly tried to fix this little issue that seems to bug others - and I've come to the conclusion that I just don't care that much myself....

The thing is, is any sort of 'organized Zen' with other people even possible with this particular character trait? Do you just endeavor to keep trying to be good at something at which you are REALLY, really bad? Don't get me wrong....if you suck at meditating, you keep doing it because - well, it's the only game in town really. Still, it's just you and the bench/cushion/chair/etc.

Hmmmrrrphh...