Well I'm tired this evening but had a great day

Practicing my classical guitar today and it was a struggle. I try and read, say and play the notes and today I couldn't do that so save my soul. Why is it some day's I play like Andres Segovia or Jimi Hendrix and other days I can't play a note. I slow down and take my time and keep on practicing. I'm working out of Charles Duncan's A Modern Approach to Classical Guitar. I'm taking my time teaching myself. I figure if it gets to difficult I'll take lessons but so far I'm doing ok. I'm also doing theory as well which helps with posture and hand position. I think I have a pretty good routine down. I practice an hour and a half a day three thirty minute sessions.
Well tomorrow is my hubby's birthday he doesn't like celebrating and I don't blame him neither do I. Well I think I'm going to do some reading right now I'll write again tomorrow.