Do you have a chronic illness? If you do, do you let your students know about it if it interferes with your teaching on some days? I have alternated years of letting my students know and years of not mentioning anything. I have found it can be really nice to let them know. If they know I am having a particularly symptomatic day for example, I will just let them know minimal information: "Pardon me if my fuse is a bit short today" so that they know today is not the day to push my buttons. The years I have mentioned minimal information, my students can usually see in my demeanor that I am having a particularly symptomatic day. I keep it vague, just letting them know that I have a medical condition that may cause me to need to sit down or walk around instead of standing while teaching or may make it very hard for me to deal with unnecessary noise. How do you handle your condition and how much do you let your students know if you let them know at all?