Parenting with ongoing health challenges

What is your advice for handling, and recommendations for resources, regarding parenting with ongoing health challenge?  In our family parents and primary caretakers have asthma, migraines, arthritis, and other ongoing conditions that can flare/really knock a person out for a few hours or even days. 

How do people manage this, especially with preschool age children? 

How do you describe, help your children process, and respect boundaries around pain/sensitivities?