Balance of family, work and school

The thoughts on my mind tonight are revolving around finding a nice balance between family, work and school.  I'm always amazed at the amount of time that can be taken up by any one thing that leaves no time for anything else.  My job seems to be in crisis mode about half of the time.  We manufacturer so there are always issues with breakdowns or call offs or ingredients that have to be dealt with before I can go home for the day.  If there is an overwhelming amount of problems, then the stress of work comes home with me for sure.  Mentally I bring it home and sometimes I bring actual work home that needs to be finished.  I very much enjoy my job and my husband works a job with long hours too.
Once I get home, there's all the normal stuff like making dinner and cleaning up from dinner.  Then I get to play with my daughter for a little while before she goes to bed.  I enjoy this time and struggle with it as well.  With stress from work hanging in my mind, I have found that my patience with my 3 year old is very limited.  I don't enjoy playing the same thing over and over again, but I know this is what she enjoys and needs for her development right now.
Add to all this, school work.  If it was just going to class, that would not be too bad.  One night a week out at class while my daughter and husband get to bond is not a bad thing.  The tough decisions come into play when my daughter goes to bed at night.  This is the brief amount of time that I have to accomplish whatever I need to get done.  This is sometimes work, sometimes school work and sometimes taking care of my home.
How does all this stay in balance?  My husband is very understanding and knows that this stress is temporary.  It lasts for a semester then there is relief for a few weeks before it begins again.  Do I spend my small amount of time on things for work or school?  Do either of these items cut into my time with my daughter?  I pretty much hold that time for her since I work all day, but how do I make this time relaxing and not stressful?  Many questions to answer as a working mother and wife.