I feel guilty

I gave notice, my last day is actually at the end of February. I wish I could wait until the end of the school year but I am so burnt out that I have no energy left for my job. My mental and physical health are being affected by this job. I have been in this school for over 20 years and in the profession since I graduated college, almost 42 years total. The school hasn’t told the parents yet and they still haven’t started interviews for my replacement. Why do I feel guilty about leaving?