You Can(not) Have it All

"Work, Marriage, Kids...at any given point, you can only give your all to two"

This is what crystalgeek78 said in the comments of today's Motherlode post "Preparing to be torn."
Some serious ink has been spilled over this topic, and I have to say, I'm struggling with this right now. How many ways can space and time be folded so that you can fulfill all of your obligations?
Do I need to (wo)man up and make it work? If I prioritize and organize correctly, can't I find a way for my will?
Or
Is it unrealistic to push myself in that way? Should I stop pressuring myself and give myself some room to suck in one arena to the benefit of another?