Having been one of those people referred to in the beginning of this thread.....simply put, you just do. You do what you have to do to make it all work....It does help that I'm not married and have no children.
Now that I'm out of school, I decided in my last semester to really start paring down my activities to focus more on me. I evaluated what I get from each and what I give to each and prioritized.
Currently, I am active in Church, Delta and the Urban League Young Professionals. Everything else is extremely secondary.
If I get bored from not being in school, watch the activities list grow again