How do they do it?

I have a hard time turning my brain off of all the 'what ifs', 'what I need to do', and 'oh crap, I forgot to do that' thoughts. Sometimes it really bothers me that I just can't enjoy my moments of silence or just some down time. It's especially frustrating when it's on one of my runs that I so desperately have a hard time getting out and doing in the first place. I often wonder whether it be on a run or during a little stretching session at home or DVD workout, how do they do it? And by 'they' I mean, how do other moms, working or SAHM, get out there and do it all when you have been up all night with a little one--especially when it's several nights in a row?
This is more of my vent, or whine if you will of the past 2 weeks or so. First it was me that caught some bug. I lost my voice for probably the 2nd time in my life and with it came an annoying tickle cough (annoying enough to have me use my stinking inhaler that I hate). Finally got some life back in me and last week made it back out there. Then kiddo #1 has a growth spurt...a pretty big one and with that comes a week or so of not-so-great sleep. We have these cycles every few months and I should be used to them but I'm not. And if the ultra crap-tastic sleep weren't enough, now kiddo #1 has the beginnings of a yet another bug.
So I ask, how do they do it? I'm getting super crappy sleep, have one super needy, clingy and sick kiddo, and another kiddo who just feeds off it and wants more attention than the other. I feel like I'm in a constant battle of trying to balance who gets what first and that always leads to me giving up something for myself. I feel incredibly guilty if I choose to do something for myself for 15 minutes. I know that I am harder on myself than I should be, but I just want to see an end in sight for all the crappy bumps that are screwing with my training plans. I know I still have time, but dangnabit, I'm impatient. And a worrier. And knowing there is a goal to reach and time slipping away from me I can't help but continue to think about how do they do it?