Living with the guilt

Of becoming a better person. 
I"m working for my grad degree.  IN Clinical Psychology.  It is a very intense 60 hour program.  I write papers, go to night class and try to balance my life around what I need to get done.
With the husband deployed, I have to count on friends to help out.  Its hard.  I hate asking for help, but at the same time, I have been set back in MY plans for years while we concentrated on my husbands career.  But what about me?  I wanted to be on the 4 year plan for my undergrad, but the every 2 year PCS, I was glad it ONLY took 6 years to finish.  Taking a term off here or there so that I could move the family, get the kid set in school, set up the house.
Now I"m one year, ONE year away from having my dream.  And the husband is gone.  So I have to worry about how I can get the kids to their sitters, make sure that the dog is taken care of and then drive almost 3 hours for a class.  And I got a hotel.  That is where the guilt starts.  I didn't have my babies.  I left them.  I knew that they were being taken care of, but still that thought is there.
Do I really need to finish school?  Its so hard as a single parent.  Staying up really late to get all the papers done, make sure that everything is taken care of in the house.  Making sure that my boys have everything that they need.  And then more studying.  Have comps, classes and soon national tests to make sure that I know what I need to before I start to practice.
But the boys understand right?  How do you explain it to a 2 year old?  Or a 13 year old?  To that little part of me that calls me selfish and tells me to drop and just worry about the kids... I can always start over in 17 years when the baby leaves...
I feel so selfish...