It's quite difficult for me; I'm sure other moms and dads are better at it than I am. I go to college full-time as a biology student, which requires a LOT of studying time (I often study on the bus or with a "sleepy-but-refuses-to-sleep-at-3-in-the-morning" toddler on one hip and my book/s on the counter so I can read and rock at the same time). I'm also working part-time in retail which is fun to juggle into the schedule since I can't work past 3 in the afternoon due to the kids' dad needing to work as well (we currently have no daycare so we each care for the kids as the other needs to go to work and/or school). The hardest part for me is finding more time to have fun. I usually have to schedule special things in (like visiting museums, hiking, etc.) so that the kids don't ever feel lost in the chaos of a busy household and also so that I remember to relax every once in a while.
*Take away: Plan and schedule as much as you feel you need to in order to be comfortable, but remember to be flexible!